A129873 Sequence s_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition).

2, 3, 8, 13, 38, 64, 196, 337, 1062, 1851, 5948, 10468, 34120, 60488, 199316, 355369, 1181126, 2115577, 7080928, 12731141, 42860534, 77306428, 261542752, 473018396, 1607076200, 2913321828, 9934255472, 18045744424, 61732449648, 112340143632

Offset

1,1

References

Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864.

Links

Table of n, a(n) for n=1..30.

Formula

See Quaintance reference for generating functions that produce A129872-A129886.

G.f.: S(t) satisfies (8*t^4 - t^2)*S(t)^3 + (24*t^3 - 2*t^2 - 4*t)*S(t)^2 + (24*t^2 + 2^t - 3)*S(t) + 8*t + 3 = 0. - Michel Marcus, Mar 29 2013

Prog

(PARI) listsn(m) = {my(S = t*O(t)); for (n= 1, m+1, S = (- 8*t - 3 - (8*t^4 - t^2)*S^3 - (24*t^3 - 2*t^2 - 4*t)*S^2)/(24*t^2 + 2*t - 3); ); return(vector(m, i , polcoeff(S, i, t))); } \\ Michel Marcus, Mar 29 2013

Crossrefs

Sequence in context: A366020 A294151 A294566 * A025575 A077055 A327868

Adjacent sequences: A129870 A129871 A129872 * A129874 A129875 A129876

Keyword

nonn

Author

N. J. A. Sloane, May 26 2007

Extensions

More terms from Michel Marcus, Mar 29 2013

Status

approved