Voozh

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

(list; graph; refs; listen; history; text; internal format)

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 ...

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

URL: https://oeis.org/A104708

⇱ A104708 - OEIS