The On-Line Encyclopedia of Integer Sequences (OEIS)

The OEIS is supported by the many generous donors to the OEIS Foundation.

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”).

Other ways to Give

A128488 revision #9

A128488

a(n) = sum of terms in n-th row of irregular table A128487.

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Table of n, a(n) for n=1..52.

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

Cf. A126080, A128487.

Sequence in context: A222136 A339652 A279787 * A359366 A226303 A117781