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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)