A060780 a(n) = gcd(sigma(n+1), sigma(n)) = gcd(A000203(n+1), A000203(n)).

1, 1, 1, 1, 6, 4, 1, 1, 1, 6, 4, 14, 2, 24, 1, 1, 3, 1, 2, 2, 4, 12, 12, 1, 1, 2, 8, 2, 6, 8, 1, 3, 6, 6, 1, 1, 2, 4, 2, 6, 6, 4, 4, 6, 6, 24, 4, 1, 3, 3, 2, 2, 6, 24, 24, 40, 10, 30, 12, 2, 2, 8, 1, 1, 12, 4, 2, 6, 48, 72, 3, 1, 2, 2, 4, 4, 24, 8, 2, 1, 1, 42, 28, 4, 12, 12, 60, 90, 18, 2, 56, 8

Offset

1,5

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Maple

seq(igcd(numtheory:-sigma(n+1), numtheory:-sigma(n)), n=1..100); # Robert Israel, Jul 03 2017

Mathematica

Table[GCD[DivisorSigma[1, n + 1], DivisorSigma[1, n]] , {n, 1, 50}] (* G. C. Greubel, Jul 03 2017 *)

Prog

(PARI) t=1; for (n=1, 1000, s=sigma(n+1); write("b060780.txt", n, " ", gcd(s, t)); t=s) \\ Harry J. Smith, Jul 11 2009

Crossrefs

Cf. A000203, A058075.

Sequence in context: A021160 A354887 A357016 * A199391 A106333 A104748

Adjacent sequences: A060777 A060778 A060779 * A060781 A060782 A060783

Keyword

nonn

Author

Labos Elemer, Apr 26 2001

Extensions

Name corrected by Robert Israel, Jul 03 2017

Status

approved