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Search: a161828 -id:a161828
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First differences of A161828.
+20
3
0, 3, 0, 6, 0, 6, 6, 12, 6
OFFSET
1,2
LINKS
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jun 21 2009
STATUS
approved
a(n) = A161828(n)/3.
+20
3
0, 0, 1, 1, 3, 3, 5, 7, 11, 13
OFFSET
0,5
LINKS
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jun 21 2009
STATUS
approved
a(n) = A161828(n)*2/3.
+20
0
0, 0, 2, 2, 6, 6, 10, 14, 22, 26
OFFSET
0,3
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jul 17 2009
STATUS
approved
Number of triangles in the Y-toothpick structure after n rounds.
+10
5
0, 0, 0, 0, 6, 6, 12, 12, 24, 30
OFFSET
0,5
LINKS
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jun 21 2009
STATUS
approved
Number of concave-convex hexagons in the Y-toothpick structure of A160120 after n rounds.
+10
5
0, 0, 0, 0, 3, 3, 3, 3, 9, 15
OFFSET
0,5
LINKS
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
KEYWORD
more,nonn
AUTHOR
Omar E. Pol, Jun 21 2009
STATUS
approved
Total number of polygons after n-th stage in the D-toothpick structure of A194270.
+10
4
0, 0, 0, 0, 2, 8, 14, 16, 26, 38, 46, 48, 56, 72, 102
OFFSET
0,5
COMMENTS
The structure of the D-toothpick cellular automaton contains at least several tens of different types of polygons. For more information see A194276 and A194277.
EXAMPLE
Consider the structure with toothpicks of length 2 and D-toothpicks of length sqrt(2). After 3 stages the number of polygons in the structure is equal to 0. After 4 stages there are 2 hexagons, each with area = 6, so a(4) = 2. After 5 stages there are new 6 polygons: 2 hexagons, each with area = 8 and also 2 octagons, each with area = 14, so a(5) = 2+6 = 8.
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Aug 26 2011
STATUS
approved
Complement of A006446.
+10
2
5, 7, 10, 11, 13, 14, 17, 18, 19, 21, 22, 23, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 78, 79, 82, 83, 84, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 96, 97, 98
OFFSET
1,1
COMMENTS
The asymptotic density of this sequence is 1 (Cooper and Kennedy, 1989). - Amiram Eldar, Jul 10 2020
LINKS
Curtis N. Cooper and Robert E. Kennedy, Chebyshev's inequality and natural density, Amer. Math. Monthly, Vol. 96, No. 2 (1989), pp. 118-124.
Omar E. Pol, Divisors and pi(x)
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Jun 21 2009, Jun 28 2009, Feb 08 2010
EXTENSIONS
More terms from N. J. A. Sloane, Feb 08 2010
STATUS
approved
Triangle read by rows in which row n lists the divisors of n, the n-th prime and the consecutive composites that are greater than the n-th prime, with a(0)=1.
+10
2
1, 1, 2, 1, 2, 3, 4, 1, 3, 5, 6, 1, 2, 4, 7, 8, 9, 10, 1, 5, 11, 12, 1, 2, 3, 6, 13, 14, 15, 16, 1, 7, 17, 18, 1, 2, 4, 8, 19, 20, 21, 22, 1, 3, 9, 23, 24, 25, 26, 27, 28, 1, 2, 5, 10, 29, 30, 1, 11, 31, 32, 33, 34, 35, 36, 1, 2, 3, 4, 6, 12, 37, 38, 39, 40
OFFSET
0,3
EXAMPLE
Triangle begins:
1;
1,(2);
1,.2,(3),4;
1,....3,...(5),6;
1,.2,....4,......(7),8,.9,10;
1,..........5,..............(11),12;
1,.2,.3,.......6,..................(13),14,15,16;
1,................7,............................(17),18;
1,.2,....4,..........8,................................(19),20,21,22;
KEYWORD
easy,nonn,tabf
AUTHOR
Omar E. Pol, Jun 30 2009
STATUS
approved
Partial sums of A056737.
+10
0
0, 1, 3, 3, 7, 8, 14, 16, 16, 19, 29, 30, 42, 47, 49, 49, 65, 68, 86, 87, 91, 100, 122, 124, 124, 135, 141, 144, 172, 173, 203, 207, 215, 230, 232, 232, 268, 285, 295, 298, 338, 339, 381, 388, 392, 413, 459, 461, 461, 466, 480, 489, 541, 544, 550, 551, 567, 594
OFFSET
1,3
FORMULA
a(n) = A219730(n) - A219729(n). - Tamas Sandor Nagy, Jan 20 2024
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jun 21 2009
EXTENSIONS
Extended beyond a(16) by R. J. Mathar, Aug 01 2009
STATUS
approved
Triangle read by rows in which row n lists the divisors of n, prime(n), the consecutive composites that are greater than prime(n), and prime (n+1), but row 0 is formed by 1 and 2.
+10
0
1, 2, 1, 2, 3, 1, 2, 3, 4, 5, 1, 3, 5, 6, 7, 1, 2, 4, 7, 8, 9, 10, 11, 1, 5, 11, 12, 13, 1, 2, 3, 6, 13, 14, 15, 16, 17, 1, 7, 17, 18, 19, 1, 2, 4, 8, 19, 20, 21, 22, 23, 1, 3, 9, 23, 24, 25, 26, 27, 28, 29, 1, 2, 5, 10, 29, 30, 31
OFFSET
0,2
COMMENTS
See also A162190, a sequence with a similar structure.
EXAMPLE
Triangle begins:
1,(2);
1,(2),(3);
1,.2.,(3),4,(5);
1,.....3,...(5),6,(7);
1,.2,.....4,......(7),8,.9,10,(11);
1,...........5,...............(11),12,(13);
1,.2,..3,.......6,....................(13),14,15,16,(17);
1,.................7,...............................(17),18,(19);
1,.2,.....4,..........8,....................................(19),20,21,22,(23);
KEYWORD
easy,nonn,tabf
AUTHOR
Omar E. Pol, Jun 30 2009
STATUS
approved

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