[go: up one dir, main page]

login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A128488 revision #10

A128488
a(n) = sum of terms in n-th row of irregular table A128487.
2
0, 1, 3, 4, 10, 9, 21, 16, 27, 25, 55, 36, 78, 49, 45, 64, 136, 81, 171, 100, 84, 121, 253, 144, 250, 169, 243, 196, 406, 105, 465, 256, 198, 289, 175, 324, 666, 361, 273, 400, 820, 189, 903, 484, 405, 529, 1081, 576, 1029, 625, 459, 676
OFFSET
1,3
FORMULA
a(n) = n *A126080(n)/2, for all n >= 1.
PROG
(PARI) as(n) = my(f=factor(n)); vecsum(Vec(select(x->(x==1), vector(n-1, j, sum(k=1, #f~, gcd(j, f[k, 1]) == 1)), 1))); \\ Michel Marcus, Oct 25 2017
CROSSREFS
Sequence in context: A222136 A339652 A279787 * A359366 A226303 A117781
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 04 2007
EXTENSIONS
More terms from R. J. Mathar, Oct 08 2007
a(1)=0 prepended by Michel Marcus, Oct 25 2017
STATUS
approved