A339353 - OEIS

A339353

G.f.: Sum_{k>=1} k^2 * x^(k*(k + 1)) / (1 - x^k).

0, 1, 1, 1, 1, 5, 1, 5, 1, 5, 1, 14, 1, 5, 10, 5, 1, 14, 1, 21, 10, 5, 1, 30, 1, 5, 10, 21, 1, 39, 1, 21, 10, 5, 26, 30, 1, 5, 10, 46, 1, 50, 1, 21, 35, 5, 1, 66, 1, 30, 10, 21, 1, 50, 26, 70, 10, 5, 1, 91, 1, 5, 59, 21, 26, 50, 1, 21, 10, 79, 1, 130, 1, 5, 35, 21, 50, 50, 1, 110

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OFFSET

1,6

COMMENTS

Sum of squares of divisors of n that are smaller than sqrt(n).

LINKS

Table of n, a(n) for n=1..80.

Index entries for sequences related to sums of divisors

MATHEMATICA

nmax = 80; CoefficientList[Series[Sum[k^2 x^(k (k + 1))/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest

Table[DivisorSum[n, #^2 &, # < Sqrt[n] &], {n, 80}]

PROG