A129880 Sequence d_n arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition).

1, 1, 4, 10, 32, 101, 334, 1129, 3890, 13618, 48275, 172995, 625574, 2279997, 8366553, 30885640, 114620926, 427383918, 1600323161, 6015226752, 22687991095, 85843131701, 325734335544, 1239274254094, 4726359853214, 18065978123065

Offset

1,3

Links

Table of n, a(n) for n=1..26.

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

Formula

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

G.f.: D(t) satisfies (t^3 + t^2)*D^3 + (t^3 - t^2 - 2*t)*D^2 + (-t^2 - t + 1)*D - t = 0. Michel Marcus, Mar 29 2013

Prog

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

Crossrefs

Sequence in context: A001673 A017936 A033297 * A303832 A316103 A137954

Adjacent sequences: A129877 A129878 A129879 * A129881 A129882 A129883

Keyword

nonn

Author

N. J. A. Sloane, May 26 2007

Status

approved