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Decimal expansion of (297 + 68*sqrt(2))/281.
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4
1, 3, 9, 9, 1, 6, 9, 1, 1, 8, 2, 9, 6, 6, 9, 2, 0, 4, 0, 2, 7, 9, 4, 1, 2, 2, 1, 7, 9, 5, 8, 2, 1, 8, 7, 5, 2, 1, 0, 9, 3, 8, 6, 7, 8, 8, 3, 4, 7, 4, 4, 6, 5, 0, 8, 8, 1, 1, 4, 3, 8, 5, 1, 3, 1, 0, 8, 0, 7, 7, 6, 1, 0, 4, 4, 6, 3, 4, 6, 1, 8, 7, 3, 3, 7, 4, 6, 0, 3, 2, 8, 5, 9, 1, 7, 4, 2, 4, 4, 4, 6, 4, 7, 6, 1
COMMENTS
lim_{n -> infinity} b(n)/b(n-1) = (297+68*sqrt(2))/281 for n mod 3 = {1, 2}, b = A129626. lim_{n -> infinity} b(n)/b(n-1) = (297+68*sqrt(2))/281 for n mod 3 = {0, 2}, b = A157348.
FORMULA
(297 + 68*sqrt(2))/281 = (17 + 2*sqrt(2))/(17 - 2*sqrt(2)).
EXAMPLE
(297 + 68*sqrt(2))/281 = 1.39916911829669204027...
MATHEMATICA
RealDigits[(297 + 68*Sqrt[2])/281, 10, 100][[1]] (* G. C. Greubel, Feb 01 2018 *)
Decimal expansion of (130803 + 73738*sqrt(2))/281^2.
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4
2, 9, 7, 7, 2, 2, 0, 1, 4, 2, 3, 7, 7, 4, 6, 8, 4, 0, 4, 7, 6, 3, 6, 0, 3, 8, 4, 4, 2, 4, 9, 3, 7, 2, 6, 8, 9, 2, 7, 1, 5, 4, 5, 0, 0, 0, 0, 1, 9, 5, 7, 1, 6, 4, 9, 5, 4, 7, 2, 7, 0, 3, 0, 4, 5, 8, 0, 2, 4, 3, 8, 1, 0, 1, 9, 5, 3, 9, 8, 3, 4, 6, 4, 0, 8, 3, 5, 1, 9, 2, 0, 6, 4, 7, 5, 5, 5, 5, 5, 6, 4, 1, 8, 1, 6
COMMENTS
lim_{n -> infinity} b(n)/b(n-1) = (130803+73738*sqrt(2))/281^2 for n mod 3 = 0, b = A129626. lim_{n -> infinity} b(n)/b(n-1) = (130803+73738*sqrt(2))/281^2 for n mod 3 = 1, b = A157348.
FORMULA
(130803 + 73738*sqrt(2))/281^2 = (458 + 161*sqrt(2))/(458 - 161*sqrt(2)) = (3 + 2*sqrt(2))*(17 - 2*sqrt(2))^2/(17 + 2*sqrt(2))^2.
EXAMPLE
(130803 + 73738*sqrt(2))/281^2 = 2.97722014237746840476...
MATHEMATICA
RealDigits[(130803 + 73738*Sqrt[2])/281^2, 10, 100][[1]] (* G. C. Greubel, Feb 01 2018 *)
PROG
(PARI) (130803+73738*sqrt(2))/281^2 \\ G. C. Greubel, Feb 01 2018 (Magma) (130803+73738*Sqrt(2))/281^2 // G. C. Greubel, Feb 01 2018
Positive numbers y such that y^2 is of the form x^2+(x+281)^2 with integer x.
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229, 281, 365, 1009, 1405, 1961, 5825, 8149, 11401, 33941, 47489, 66445, 197821, 276785, 387269, 1152985, 1613221, 2257169, 6720089, 9402541, 13155745, 39167549, 54802025, 76677301, 228285205, 319409609, 446908061, 1330543681
COMMENTS
(-60, a(1)) and ( A129626(n), a(n+1)) are solutions (x, y) to the Diophantine equation x^2+(x+281)^2 = y^2.
FORMULA
a(n) = 6*a(n-3)-a(n-6) for n > 6; a(1)=229, a(2)=281, a(3)=365, a(4)=1009, a(5)=1405, a(6)=1961.
G.f.: x*(1-x)*(229+510*x+875*x^2+510*x^3+229*x^4) / (1-6*x^3+x^6).
a(3*k-1) = 281* A001653(k) for k >= 1. Limit_{n -> oo} a(n)/a(n-3) = 3+2*sqrt(2).
Limit_{n -> oo} a(n)/a(n-1) = (297+68*sqrt(2))/281 for n mod 3 = {0, 2}.
Limit_{n -> oo} a(n)/a(n-1) = (130803+73738*sqrt(2))/281^2 for n mod 3 = 1.
EXAMPLE
(-60, a(1)) = (-60, 229) is a solution: (-60)^2+(-60+281)^2 = 3600+48841 = 52441 = 229^2.
( A129626(1), a(2)) = (0, 281) is a solution: 0^2+(0+281)^2 = 78961 = 281^2. ( A129626(3), a(4)) = (559, 1009) is a solution: 559^2+(559+281)^2 = 312481+705600 = 1018081 = 1009^2.
PROG
(PARI) {forstep(n=-60, 200000000, [3, 1], if(issquare(2*n^2+562*n+78961, &k), print1(k, ", ")))}
CROSSREFS
Cf. A129626, A001653, A156035 (decimal expansion of 3+2*sqrt(2)), A157349 (decimal expansion of (297+68*sqrt(2))/281), A157350 (decimal expansion of (130803+73738*sqrt(2))/281^2).
Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+2737)^2 = y^2.
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0, 75, 203, 323, 552, 708, 1020, 1127, 1311, 1428, 1608, 1820, 1955, 2336, 2675, 3128, 3311, 3627, 3927, 4140, 4508, 4743, 5535, 6003, 6800, 7280, 7848, 8211, 8588, 9240, 9860, 11063, 11895, 13583, 14168, 15180, 15827, 16827, 18011, 18768, 20915, 22836
COMMENTS
Note that 2737 = 7 * 17 * 23, the product of the first three distinct primes in A058529 (and A001132) and hence the smallest such number. This sequence satisfies a linear difference equation of order 55 whose 55 initial terms can be found by running the Mathematica program. There are many sequences like this one. What determines the order of the linear difference equation? All primes p have order 7. For those p, it appears that p^2 has order 11, p^3 order 15, and p^i order 3+4*i. It appears that for semiprimes p*q (with p > q), the order is 19. What is the next term of the sequence beginning 3, 7, 19, 55, 163? This could be sequence A052919, which is 1 + 2*3^f, where f is the number of primes. The crossref list is thought to be complete up to Feb 14 2012.
FORMULA
a(n) = a(n-1) + 6*a(n-27) - 6*a(n-28) - a(n-54) + a(n-55), where the 55 initial terms can be computed using the Mathematica program.
G.f.: x^2*(73*x^53 +116*x^52 +100*x^51 +171*x^50 +104*x^49 +184*x^48 +57*x^47 +92*x^46 +55*x^45 +80*x^44 +88*x^43 +53*x^42 +139*x^41 +113*x^40 +139*x^39 +53*x^38 +88*x^37 +80*x^36 +55*x^35 +92*x^34 +57*x^33 +184*x^32 +104*x^31 +171*x^30 +100*x^29 +116*x^28 +73*x^27 -363*x^26 -568*x^25 -480*x^24 -797*x^23 -468*x^22 -792*x^21 -235*x^20 -368*x^19 -213*x^18 -300*x^17 -316*x^16 -183*x^15 -453*x^14 -339*x^13 -381*x^12 -135*x^11 -212*x^10 -180*x^9 -117*x^8 -184*x^7 -107*x^6 -312*x^5 -156*x^4 -229*x^3 -120*x^2 -128*x -75) / ((x -1)*(x^54 -6*x^27 +1)). - Colin Barker, May 18 2015
MATHEMATICA
d = 2737; terms = 100; t = Select[Range[0, 55000], IntegerQ[Sqrt[#^2 + (#+d)^2]] &]; Do[AppendTo[t, t[[-1]] + 6*t[[-27]] - 6*t[[-28]] - t[[-54]] + t[[-55]]], {terms-55}]; t
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