

A193334


Number of even divisors of sigma(n).


2



0, 0, 2, 0, 2, 4, 3, 0, 0, 3, 4, 4, 2, 6, 6, 0, 3, 0, 4, 4, 5, 6, 6, 8, 0, 4, 6, 6, 4, 9, 5, 0, 8, 4, 8, 0, 2, 8, 6, 6, 4, 10, 4, 8, 4, 9, 8, 4, 0, 0, 9, 3, 4, 12, 9, 12, 8, 6, 8, 12, 2, 10, 6, 0, 8, 12, 4, 6, 10, 12, 9, 0, 2, 4, 4, 8
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OFFSET

1,3


COMMENTS

sigma(n) = sum of divisors of n, A000203.


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


EXAMPLE

a(14) = 6 because sigma(14) = 24 and the 6 even divisors are {2, 4, 6, 8, 12, 24}.


MATHEMATICA

f[n_] := Block[{d = Divisors[DivisorSigma[1, n]]}, Count[EvenQ[d], True]]; Table[f[n], {n, 80}]


PROG

(PARI) a(n)=n=sigma(n); if(n%2, 0, numdiv(n/2)) \\ Charles R Greathouse IV, Jul 30 2011


CROSSREFS

Cf. A000203.
Sequence in context: A023987 A021498 A025251 * A185081 A011119 A240747
Adjacent sequences: A193331 A193332 A193333 * A193335 A193336 A193337


KEYWORD

nonn


AUTHOR

Michel Lagneau, Jul 23 2011


STATUS

approved



