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A193347
Number of even divisors of tau(n).
2
0, 1, 1, 0, 1, 2, 1, 2, 0, 2, 1, 2, 1, 2, 2, 0, 1, 2, 1, 2, 2, 2, 1, 3, 0, 2, 2, 2, 1, 3, 1, 2, 2, 2, 2, 0, 1, 2, 2, 3, 1, 3, 1, 2, 2, 2, 1, 2, 0, 2, 2, 2, 1, 3, 2, 3, 2, 2, 1, 4, 1, 2, 2, 0, 2, 3, 1, 2, 2, 3, 1, 4, 1, 2, 2, 2, 2, 3, 1, 2, 0, 2, 1, 4, 2, 2, 2, 3, 1, 4, 2, 2, 2, 2, 2, 4, 1, 2, 2, 0, 1, 3, 1, 3, 3, 2, 1, 4, 1, 3, 2, 2, 1, 3
OFFSET
1,6
LINKS
FORMULA
a(n) = A183063(A000005(n)). - Antti Karttunen, May 28 2017
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