OFFSET
1,2
COMMENTS
Inverse Möbius transform of A306682. - Antti Karttunen, May 09 2020
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537
FORMULA
a(p) = 2 for p = primes (A000040).
EXAMPLE
a(6) = gcd(sigma(1), pod(1)) + gcd(sigma(2), pod(2)) + gcd(sigma(3), pod(3)) + gcd(sigma(6), pod(6)) = gcd(1, 1) + gcd(3, 2) + gcd(4, 3) + gcd(12, 36) = 1 + 1 + 1 + 12 = 15.
PROG
(Magma) [&+[GCD(&+Divisors(d), &*Divisors(d)): d in Divisors(n)]: n in [1..100]]
(PARI) a(n) = sumdiv(n, d, gcd(sigma(d), vecprod(divisors(d)))); \\ Michel Marcus, May 08 2020
CROSSREFS
Cf. A334731 (product instead of sum).
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, May 07 2020
STATUS
approved