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A082397
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Number of directed aggregates of height <= 2 with n cells.
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0
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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; internal format)
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OFFSET
| 1,2
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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.
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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 (vladeta(AT)eunet.rs), Sep 18 2003
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CROSSREFS
| Sequence in context: A191692 A124217 A095981 * A051286 A192475 A192400
Adjacent sequences: A082394 A082395 A082396 * A082398 A082399 A082400
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KEYWORD
| nonn
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AUTHOR
| Fouad IBN MAJDOUB HASSANI (fouad.ibnmajdoubhassani(AT)wanadoo.fr), Apr 14 2003
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 18 2003
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