A372565 a(n) is the greatest common divisor of n, sigma(n) and A003961(n), where A003961(n) is fully multiplicative function with a(prime(i)) = prime(i+1).

1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1

Offset

1,6

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 sigma(n)

Prog

(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A372565(n) = gcd([n, sigma(n), A003961(n)]);

Crossrefs

Cf. A000203, A003961, A372566 (positions of terms > 1).

Greatest common divisor of any two of the following: A009194, A322361, A342671.

Sequence in context: A202150 A093818 A097031 * A354997 A327537 A120263

Adjacent sequences: A372562 A372563 A372564 * A372566 A372567 A372568

Keyword

nonn,easy

Author

Antti Karttunen, May 19 2024

Status

approved