

A195207


Number of even divisors of !n.


2



0, 0, 0, 1, 0, 4, 0, 6, 0, 24, 0, 4, 0, 24, 0, 4, 0, 16, 0, 24, 0, 32, 0, 96, 0, 144, 0, 16, 0, 64, 0, 144, 0, 40, 0, 128, 0, 160, 0, 16, 0, 96, 0, 96, 0, 32, 0, 128, 0, 96, 0, 48, 0, 128, 0, 96, 0, 96, 0, 32, 0
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OFFSET

0,6


COMMENTS

!n is a subfactorial number (A000166).
Property of this sequence : for n different of 3, the number of even divisors of !n seems even.


LINKS

Table of n, a(n) for n=0..60.


EXAMPLE

a(7) = 6 because the divisors of !7 = 1854 are {1, 2, 3, 6, 9, 18, 103, 206, 309, 618, 927, 1854}with 6 even divisors 2, 6, 18, 206, 618, 1854 => 6 is in the sequence.


MATHEMATICA

f[n_] := Block[{d = Divisors[Subfactorial[n]]}, Count[EvenQ[d], True]]; Table[f[n], {n, 0, 60}]


CROSSREFS

Cf. A000166, A195208.
Sequence in context: A023891 A075091 A132953 * A157721 A085968 A010637
Adjacent sequences: A195204 A195205 A195206 * A195208 A195209 A195210


KEYWORD

nonn


AUTHOR

Michel Lagneau, Sep 13 2011


STATUS

approved



