A290046 a(n) = |Sum_{k=0..n} (-1)^k*(3k)!!|.

1, 2, 46, 899, 45181, 1981844, 183812716, 13565497859, 1948425055741, 11509621621134, 42638364069002866, 6290021506693847759, 1672053831207666984241, 318158932941670103831384, 106827312624343125411048616, 25266964023001914822246560759

Offset

0,2

Comments

a(26) = 2 * 41 * 121157 * 160215276888781 * 1706504288791033 * 4123576055576581869533. Thus a(n) are multiples of 41 for n >= 26.

Links

Table of n, a(n) for n=0..15.

Mathematica

Table[Abs@ Sum[(-1)^k*(3 k)!!, {k, 0, n}], {n, 0, 15}] (* Michael De Vlieger, Jul 19 2017 *)

Crossrefs

Cf. A006882, A138525.

Sequence in context: A302949 A174592 A066555 * A012001 A012006 A279524

Adjacent sequences: A290043 A290044 A290045 * A290047 A290048 A290049

Keyword

easy,nonn

Author

XU Pingya, Jul 19 2017

Status

approved