A195210 Sum of odd divisors of !n.

1, 0, 1, 1, 13, 12, 324, 1352, 18368, 19152, 1994322, 8810748, 193690826, 829046868, 34563283272, 274895151856, 14554448767872, 8178592487376, 2493850026398472, 33842416675133248, 1037660717168380800, 6072370562498569056

Offset

0,5

Comments

!n is a subfactorial number (A000166).

Property of the sequence: for n> 4 the sum of odd divisors of !n seems even.

Links

Table of n, a(n) for n=0..21.

Example

a(7) = 1352 because the divisors of  !7 = 1854 are  {1, 2, 3, 6, 9, 18, 103, 206, 309, 618, 927, 1854}, and the sum of the 6  odd divisors  1, 3, 9, 103, 309 and 927 is 1352.

Mathematica

Table[Total[Select[Divisors[Subfactorial[n]], OddQ[ # ]&]], {n, 0, 21}]

Crossrefs

Cf. A000166, A195208.

Sequence in context: A004454 A113548 A249998 * A175850 A176306 A291368

Adjacent sequences: A195207 A195208 A195209 * A195211 A195212 A195213

Keyword

nonn

Author

Michel Lagneau, Sep 13 2011

Status

approved