A342673 a(n) = gcd(n, sigma(A003961(n))), where A003961 is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors of n.

1, 2, 3, 1, 1, 6, 1, 8, 1, 2, 1, 6, 1, 2, 3, 1, 1, 2, 1, 4, 3, 2, 1, 24, 1, 2, 3, 4, 1, 6, 1, 4, 3, 2, 1, 1, 1, 2, 3, 40, 1, 6, 1, 2, 1, 2, 1, 6, 7, 2, 3, 26, 1, 6, 1, 8, 3, 2, 1, 12, 1, 2, 3, 1, 1, 6, 1, 4, 3, 2, 1, 8, 1, 2, 3, 4, 7, 6, 1, 8, 1, 2, 1, 12, 5, 2, 3, 8, 1, 2, 1, 2, 3, 2, 1, 24, 1, 14, 1, 1, 1, 6, 1, 8, 3

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Formula

a(n) = gcd(n, A003973(n)) = gcd(n, A000203(A003961(n))).

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A342673(n) = gcd(n, sigma(A003961(n)));

Crossrefs

Cf. A000203, A003961, A003973, A342671.

Cf. also A336850, A341528.

Sequence in context: A011151 A140878 A182933 * A365463 A068348 A308290

Adjacent sequences: A342670 A342671 A342672 * A342674 A342675 A342676

Keyword

nonn

Author

Antti Karttunen, Mar 20 2021

Status

approved