A353751 - OEIS

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A353751

a(n) = gcd(n, sigma(sigma(n))), where sigma is the sum of divisors function.

1, 2, 1, 4, 1, 2, 1, 8, 1, 1, 1, 4, 1, 2, 15, 16, 1, 2, 1, 4, 21, 1, 1, 24, 1, 2, 9, 4, 1, 15, 1, 8, 1, 2, 1, 4, 1, 2, 3, 2, 1, 42, 1, 4, 3, 1, 1, 16, 1, 2, 3, 1, 1, 18, 5, 8, 3, 2, 1, 60, 1, 2, 21, 64, 1, 1, 1, 4, 3, 1, 1, 24, 1, 2, 1, 4, 7, 6, 1, 16, 1, 2, 1, 84, 5, 2, 3, 2, 1, 6, 1, 4, 3, 1, 5, 8, 1, 2, 1, 4

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..100.

Index entries for sequences related to sigma(n)

FORMULA

a(n) = gcd(n, A051027(n)).

a(n) = A051027(n) / A318059(n) = n / A318060(n).

PROG

(PARI) A353751(n) = gcd(n, sigma(sigma(n)));

CROSSREFS