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Search: id:A024283
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| A024283 |
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Expansion of tan(x)^2/2. |
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+0
4
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| 0, 1, 8, 136, 3968, 176896, 11184128, 951878656, 104932671488, 14544442556416, 2475749026562048, 507711943253426176, 123460740095103991808, 35125800801971979943936, 11559592093904798920736768
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Number of cyclically reverse alternating permutations of length 2n+1, cf. A024255. - Vladeta Jovovic (vladeta(AT)eunet.rs), May 20 2007
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REFERENCES
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L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 259, T(n,2).
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EXAMPLE
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(tan x)^2 = x^2 + 2/3*x^4 + 17/45*x^6 + 62/315*x^8 + ...
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MATHEMATICA
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Tan[ x ]^2/2 (* Even Part *)
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CROSSREFS
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A009764.
Cf. A009764, A000182. A diagonal of A059419.
Sequence in context: A132869 A036915 A049211 this_sequence A134053 A136472 A145404
Adjacent sequences: A024280 A024281 A024282 this_sequence A024284 A024285 A024286
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KEYWORD
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nonn,easy
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AUTHOR
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R. H. Hardin (rhhardin(AT)att.net)
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EXTENSIONS
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Extended and signs tested 03/97.
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