A127021 Number of rhyme schemes (see reference for precise definition).

1, 11, 80, 491, 2777, 15120, 81371, 440947, 2441334, 13976885, 83547881, 525082654, 3483272777, 24413200487, 180517606216, 1404147099951, 11449330342717, 97521479081952, 864955731435983, 7966538662094103

Offset

4,2

References

J. Riordan, A budget of rhyme scheme counts, pp. 455 - 465 of Second International Conference on Combinatorial Mathematics, New York, April 4-7, 1978. Edited by Allan Gewirtz and Louis V. Quintas. Annals New York Academy of Sciences, 319, 1979.

Links

Table of n, a(n) for n=4..23.

J. Riordan, Cached copy of paper

Formula

a(k)=1. a(n)=k*a(n-1)+A000110(n-1)-A102661(n-1,k-2), k=4.

Crossrefs

Cf. A005002, A005003.

Sequence in context: A227244 A026897 A021024 * A326243 A091098 A091115

Adjacent sequences: A127018 A127019 A127020 * A127022 A127023 A127024

Keyword

nonn

Author

R. J. Mathar, Jul 15 2008

Status

approved