A073014 (n!/2)*sum(k=1,n,(n+k)!/(k!)^3).

1, 9, 127, 2835, 93901, 4336878, 266268402, 20961918435, 2057633544961, 246291719185578, 35300219800649134, 5967365133741366446, 1174674087014062487490, 266337973265724541242428

Offset

1,2

Comments

a(n) is odd for n = 1,2,3 and if n is of the form 2^m or 2^m+1 (with m>= 2) (i.e. a(n) is odd if n=1,3,4,5,8,9,16,17,32,33,64,65,128,129,256,257...)

Links

Table of n, a(n) for n=1..14.

Prog

(PARI) a(n)=if(n<0, 0, (n!/2)*sum(k=1, n, (n+k)!/(k!)^3))

Crossrefs

Sequence in context: A258294 A362776 A365033 * A046754 A203425 A275259

Adjacent sequences: A073011 A073012 A073013 * A073015 A073016 A073017

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 03 2002

Status

approved