OFFSET
1,3
FORMULA
a(n) = n *A126080(n)/2, for all n >= 1.
PROG
(PARI) as(n) = my(f=factor(n)); vecsum(Vec(select(x->(x==1), vector(n-1, j, sum(k=1, #f~, gcd(j, f[k, 1]) == 1)), 1))); \\ Michel Marcus, Oct 25 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 04 2007
EXTENSIONS
More terms from R. J. Mathar, Oct 08 2007
a(1)=0 prepended by Michel Marcus, Oct 25 2017
STATUS
approved