OFFSET
1,1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
a(n) = Sum_{d|n} (1+gcd(2,d)+gcd(4,d)). - Antti Karttunen, Sep 30 2018
PROG
(PARI) A221951(n) = sumdiv(n, d, (1+gcd(2, d)+gcd(4, d))); \\ Antti Karttunen, Sep 30 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 02 2013
STATUS
approved