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A060780
a(n) = gcd(sigma(n+1), sigma(n)) = gcd(A000203(n+1), A000203(n)).
8
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
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
Sequence in context: A021160 A354887 A357016 * A199391 A106333 A104748
KEYWORD
nonn
AUTHOR
Labos Elemer, Apr 26 2001
EXTENSIONS
Name corrected by Robert Israel, Jul 03 2017
STATUS
approved