A104708 Product of number of involutions on n letters and number of partitions of n

1, 1, 4, 12, 50, 182, 836, 3480, 16808, 78600, 398832, 1998976, 10791704, 57418904, 322714800, 1821518336, 10673756016, 62904395664, 383965822240, 2356753705600, 14896682388192, 95002532773632, 620122408189824

Offset

0,3

Links

Table of n, a(n) for n=0..22.

Formula

A104708(n) = A000085(n) * A000041(n)

Example

A000085 begins 1 1 2 4 10 26 ...
A000041 begins 1 1 2 3 5 7 ...
so
A104708 begins 1 1 4 12 50 182 ...
a(3)=4*3=12 because there are 4 involutions of 123 (namely: 123, 132, 213 and 321) and 3 partitions of 3 (3=2+1=1+1+1).

Maple

with(combinat): b:= proc(n) option remember: if n=0 then 1 elif n=1 then 1 else b(n-1)+(n-1)*b(n-2): fi: end: c:=n->numbpart(n): seq(b(n)*c(n), n=0..25);

Crossrefs

Sequence in context: A149391 A149392 A149393 * A149394 A149395 A149396

Adjacent sequences: A104705 A104706 A104707 * A104709 A104710 A104711

Keyword

easy,nonn

Author

Alford Arnold, Mar 21 2005

Extensions

More terms from Emeric Deutsch, Mar 23 2005

Status

approved