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A104708
Product of number of involutions on n letters and number of partitions of n
1
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
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
KEYWORD
easy,nonn
AUTHOR
Alford Arnold, Mar 21 2005
EXTENSIONS
More terms from Emeric Deutsch, Mar 23 2005
STATUS
approved