A218219 Define a(x,y) to be 1 if x is 0 or 1 and y*a(x-1,y)-a(x-2,y) otherwise. Then the n-th term of the sequence is a(n,n).

1, 1, 1, 5, 41, 436, 5741, 90481, 1663585, 34988311, 828931049, 21851881930, 634556225161, 20129592507025, 692665874901013, 25699370092119569, 1022757988416562049, 43461563755791470416, 1964206882303435582865, 94076863910519354420761, 4760163616791818063701801

Offset

0,4

Comments

The sequence grows about as fast as x!*e^x/p(x), where p(x) is a quadratic.

Links

Table of n, a(n) for n=0..20.

Example

For 3, by definition, a(0,3)=1 and a(1,3)=1, so a(2,3)=3*a(1,3)-a(0,3)=3-1=2 and a(3,3)=3*a(2,3)-a(1,3)=6-1=5, so the third element is 5

Crossrefs

Cf. A218220.

Sequence in context: A285064 A232685 A081215 * A140095 A259609 A323213

Adjacent sequences: A218216 A218217 A218218 * A218220 A218221 A218222

Keyword

nonn

Author

Nico Brown, Oct 23 2012

Status

approved