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A195210 Sum of odd divisors of !n. 0
1, 0, 1, 1, 13, 12, 324, 1352, 18368, 19152, 1994322, 8810748, 193690826, 829046868, 34563283272, 274895151856, 14554448767872, 8178592487376, 2493850026398472, 33842416675133248, 1037660717168380800, 6072370562498569056 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 17 16:08 EST 2019. Contains 329241 sequences. (Running on oeis4.)