A355456 Greatest common divisor of sigma(n), A003961(n), and A276086(n).

1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 5, 1, 3, 5, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 9, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 1, 1, 5, 1, 3, 5, 3, 1, 7, 1, 3, 1, 1, 7, 1, 1, 3, 1, 3, 1, 5, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 5, 9, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 7, 1, 1, 1, 3, 1

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to primorial base

Index entries for sequences related to sigma(n)

Formula

a(n) = gcd(A000203(n), A355442(n)).

a(n) = gcd(A324644(n), A342671(n)) = gcd(A276086(n), A342671(n)) = gcd(A003961(n), A324644(n)).

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
A355442(n) = gcd(A003961(n), A276086(n));
A355456(n) = gcd(sigma(n), A355442(n));

Crossrefs

Cf. A000203, A003961, A276086, A324644, A342671, A355442, A355002 (terms k such that a(k) shares a prime factor with k).

Cf. also A323653, A351459.

Sequence in context: A336850 A061680 A382267 * A097558 A124385 A317624

Adjacent sequences: A355453 A355454 A355455 * A355457 A355458 A355459

Keyword

nonn

Author

Antti Karttunen, Jul 13 2022

Status

approved