A186428 - OEIS

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A186428

sigma(n^2) modulo sigma(n).

0, 1, 1, 3, 1, 7, 1, 7, 4, 1, 1, 11, 1, 15, 19, 15, 1, 28, 1, 37, 5, 31, 1, 31, 6, 21, 13, 31, 1, 13, 1, 31, 1, 43, 39, 20, 1, 27, 27, 67, 1, 3, 1, 7, 7, 55, 1, 71, 8, 73, 31, 87, 1, 91, 19, 39, 73, 67, 1, 61, 1, 39, 33, 63, 45, 7, 1, 67, 85, 129, 1, 157, 1, 45, 109, 51, 93, 21, 1, 31, 40, 91, 1, 123, 13, 51, 43, 151, 1, 49, 15, 7, 109, 103, 51, 151, 1, 113, 25, 124, 1, 73, 1, 141, 123, 115, 1, 3, 1, 133, 51, 111, 1, 111, 7, 121, 121

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OFFSET

1,4

COMMENTS

a(n)=1 iff n is prime. Apparently a(n)>2 for composite n's.

LINKS

Table of n, a(n) for n=1..117.

FORMULA

a(n) = A065764(n) mod A000203(n).

MATHEMATICA

Table[Mod[DivisorSigma[1, n^2], DivisorSigma[1, n]], {n, 200000}]

CROSSREFS