OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
a(24) = 3 because tau(24) = 8 and the 3 even divisors are {2, 4, 8}.
MATHEMATICA
f[n_] := Block[{d = Divisors[DivisorSigma[0, n]]}, Count[EvenQ[d], True]]; Table[f[n], {n, 80}]
PROG
(PARI) a(n)=sumdiv(sigma(n, 0), d, (1-d%2));
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jul 23 2011
STATUS
approved