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

1,9

Links

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

Formula

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A347176 A164561 A178764 * A293768 A046564 A046592

Adjacent sequences: A070007 A070008 A070009 * A070011 A070012 A070013

Keyword

nonn

Author

Labos Elemer, Apr 11 2002

Status

approved