A070010 GCD of consecutive values of sum-of-proper divisors.

1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 11, 1, 1, 1, 6, 2, 1, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 1, 1, 1, 23, 1, 1, 1, 1, 3, 1, 1, 5, 25, 1, 1, 1, 1, 3, 1, 1, 1, 1

Offset: 1

Author

Labos Elemer, Apr 11 2002

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A001065; GCD of various consecutive function values: A048586, A057467, A058515, A060778, A060780, A069896.

Programs

Mathematica

GCD[DivisorSigma[1, n+1]-(n+1), DivisorSigma[1, n]-n]

PARI

A001065(n) = (sigma(n) - n);
A070010(n) = gcd(A001065(n),A001065(1+n)); \\ Antti Karttunen, Oct 05 2017

Formula

a(n) = gcd(A001065(n+1), A001065(n)).