A378913 a(n) = sum of all positive m such that sigma(m) divides n, where sigma is the sum-of-divisors function (A000203).

1, 1, 3, 4, 1, 8, 5, 11, 3, 1, 1, 28, 10, 18, 11, 11, 1, 35, 1, 23, 7, 1, 1, 87, 1, 10, 3, 33, 1, 45, 42, 63, 3, 1, 5, 77, 1, 38, 30, 57, 1, 112, 1, 47, 11, 1, 1, 202, 5, 1, 3, 13, 1, 122, 1, 107, 52, 1, 1, 205, 1, 103, 39, 63, 10, 8, 1, 71, 3, 18, 1, 389, 1, 74, 11

Offset

1,3

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n)

Mathematica

With[{nmax = 100}, Table[Total[PositionIndex[Divisible[n, #[[;; n]]]][True]], {n, nmax}] & [DivisorSigma[1, Range[nmax]]]]

Prog

(PARI) a(n) = vecsum(select(x->(!(n % sigma(x))), [1..n])); \\ Michel Marcus, Dec 11 2024

Crossrefs

Row sums of A378912.

Cf. A378915 (positions of ones).

Cf. A000203.

Sequence in context: A324559 A174607 A326503 * A105578 A378227 A198739

Adjacent sequences: A378910 A378911 A378912 * A378914 A378915 A378919

Keyword

nonn,new

Author

Paolo Xausa, Dec 11 2024

Status

approved