A388021 - OEIS

A388021

a(n) = gcd(A276086(floor(sigma(n)/2)), A276086(n)), where A276086 is the primorial base exp-function, and sigma is the sum of divisors function.

1, 1, 3, 3, 6, 5, 1, 5, 5, 15, 5, 25, 10, 25, 25, 75, 30, 125, 5, 375, 75, 125, 25, 1, 50, 375, 375, 5625, 150, 7, 1, 7, 1, 3, 1, 35, 10, 7, 15, 105, 30, 175, 25, 175, 210, 35, 25, 7, 125, 525, 35, 875, 750, 7, 35, 7, 105, 525, 7, 49, 14, 7, 21, 147, 7, 245, 7, 147, 35, 245, 35, 245, 70, 525, 147, 2205, 175, 6125

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..11550

Index entries for sequences related to primorial base.

Index entries for sequences related to sigma(n).

FORMULA

a(n) = gcd(A276086(n), A388018(n)).

PROG

(PARI)

A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };