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A082397 Number of directed aggregates of height <= 2 with n cells. 0
1, 2, 5, 11, 26, 62, 153, 385, 988, 2573, 6786, 18084, 48621, 131718, 359193, 985185, 2715972, 7521567, 20915256, 58373586, 163462815, 459136809, 1293223230, 3651864606, 10336625731, 29321683082, 83344398533, 237344961291 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Fouad Ibn-Majdoub-Hassani. Combinatoire de polyominos et des tableaux decales oscillants . These de Doctorat. Laboratoire de Recherche en Informatique, Universite Paris-Sud XI, France.

LINKS

Table of n, a(n) for n=1..28.

FORMULA

a(n) = Sum_{k=1..n}(-1)^(k+1)*binomial(n+1, k+1)*binomial(k, floor((k-1)/2)). E.g.f.: -exp(x)*int(-BesselI(1, 2*x)+BesselI(2, 2*x), x)-exp(x)*(-BesselI(1, 2*x)+BesselI(2, 2*x)). - Vladeta Jovovic, Sep 18 2003

CROSSREFS

Sequence in context: A124217 A095981 A247471 * A051286 A192475 A192400

Adjacent sequences:  A082394 A082395 A082396 * A082398 A082399 A082400

KEYWORD

nonn

AUTHOR

Fouad IBN MAJDOUB HASSANI, Apr 14 2003

EXTENSIONS

More terms from Vladeta Jovovic, Sep 18 2003

STATUS

approved

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Last modified May 31 18:34 EDT 2020. Contains 334748 sequences. (Running on oeis4.)