A374963 a(n) = Sum_{k=1..n-1} sigma(k)*sigma_3(n-k).

0, 1, 12, 59, 200, 526, 1184, 2399, 4368, 7656, 12316, 19586, 29008, 43244, 60272, 85543, 114000, 156163, 200652, 266504, 333968, 432570, 528704, 673706, 806200, 1008644, 1192584, 1467684, 1707328, 2084676, 2390848, 2882487, 3286168, 3913722, 4409584, 5237489

Offset

1,3

Comments

Convolution of sigma with sigma_3.

Links

Table of n, a(n) for n=1..36.

Mathematica

Table[Sum[DivisorSigma[1, k] *DivisorSigma[3, n-k], {k, n-1}], {n, 36}] (* James C. McMahon, Aug 11 2024 *)

Prog

(Python)
from sympy import divisor_sigma
def A374963(n): return sum(divisor_sigma(i)*divisor_sigma(n-i, 3) for i in range(1, n))

Crossrefs

Cf. A000203, A000385, A001158.

Sequence in context: A242983 A167533 A244907 * A062477 A048362 A231215

Adjacent sequences: A374960 A374961 A374962 * A374964 A374965 A374966

Keyword

nonn,easy

Author

Chai Wah Wu, Jul 25 2024

Status

approved