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Search: id:A130168
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| 1, 3, 15, 111, 1131, 15123, 256335, 5364471, 135751731, 4084163643, 144039790455, 5884504366431, 275643776229531, 14673941326078563, 880908054392169375, 59226468571935857991, 4432461082611507366531, 367227420727722013775883, 33514867695588319595233095
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OFFSET
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2,2
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COMMENT
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As remarked by Gessel, A000366 has a combinatorial interpretation via a certain 2n X n array; this sequence is for a similar array of size (2n-1) X (n-1).
In effect, Dellac gives a combinatorial reason why the elements of A000366 are alternately -1 and +1 modulo 3. Dellac also shows that all the terms of this sequence are odd.
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REFERENCES
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Hippolyte Dellac, Note sur l'\'elimination, m\'ethode de parall\'elogramme, Annales de la Facult\'e des Sciences de Marseille, XI (1901), 141-164.
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CROSSREFS
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Cf. A000366, A130169.
Sequence in context: A142967 A112936 A001063 this_sequence A089945 A135083 A058104
Adjacent sequences: A130165 A130166 A130167 this_sequence A130169 A130170 A130171
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KEYWORD
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nonn
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AUTHOR
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D. E. Knuth, Aug 02 2007
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