A326039 - OEIS

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A326039

Largest square dividing the sum of divisors of n: a(n) = A008833(sigma(n)).

1, 1, 4, 1, 1, 4, 4, 1, 1, 9, 4, 4, 1, 4, 4, 1, 9, 1, 4, 1, 16, 36, 4, 4, 1, 1, 4, 4, 1, 36, 16, 9, 16, 9, 16, 1, 1, 4, 4, 9, 1, 16, 4, 4, 1, 36, 16, 4, 1, 1, 36, 49, 9, 4, 36, 4, 16, 9, 4, 4, 1, 16, 4, 1, 4, 144, 4, 9, 16, 144, 36, 1, 1, 1, 4, 4, 16, 4, 16, 1, 121, 9, 4, 16, 36, 4, 4, 36, 9, 9, 16, 4, 64, 144, 4, 36

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OFFSET

1,3

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences related to sigma(n)

FORMULA

a(n) = A008833(A000203(n)) = A326038(n)^2.

a(n) = A000203(n) - A326040(n).

MATHEMATICA

Module[{sqs=Range[100, 1, -1]^2}, Table[SelectFirst[sqs, Divisible[ DivisorSigma[ 1, n], #]&], {n, 100}]] (* Harvey P. Dale, Jul 29 2019 *)

PROG