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Search: id:A136659
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| A136659 |
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Unsigned third column (k=2) of triangle A136656 divided by 4. |
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+0
3
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| 1, 9, 75, 660, 6300, 65520, 740880, 9072000, 119750400, 1696464000, 25686460800, 414096883200, 7083236160000, 128152088064000, 2445351068160000, 49084865077248000, 1033983353475072000, 22808456326656000000
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OFFSET
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0,2
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COMMENT
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Also unsigned second column of triangle A136657 divided by 2.
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REFERENCES
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Ch. A. Charalambides, Enumerative Combinatorics, Chapman & Hall/CRC, Boca Raton, Florida, 2002, Table 8.3, p. 311, with s=-2, k=2 column/4.
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FORMULA
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a(n)= |A136656(n+2,2)|/4, n>=0.
E.g.f.(derived from the one given for the column k=2 under A136656): (2+6*x-3*x^2)/(2*(1-x)^6).
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CROSSREFS
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Cf. A001710 (1/2 of unsigned k=1 column of A136657). A136660 (k=3 column divided by 8).
Sequence in context: A102094 A125397 A095249 this_sequence A126965 A066222 A080254
Adjacent sequences: A136656 A136657 A136658 this_sequence A136660 A136661 A136662
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Feb 22 2008
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