OFFSET
0,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..40
FORMULA
a(n) = (1/n)*Sum_{ d divides n } phi(d)*3^(n^2/d) for n > 0.
PROG
(PARI) a(n) = if(n<1, n==0, sumdiv(n, d, eulerphi(d)*3^(n^2/d))/n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Yuval Dekel (dekelyuval(AT)hotmail.com), Jul 28 2003
EXTENSIONS
a(0)=1 prepended and terms a(7) and beyond from Andrew Howroyd, Jul 08 2018
STATUS
approved