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A165433
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A transform of the double factorial numbers A001147.
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0
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1, 1, 2, 3, 7, 14, 39, 97, 308, 897, 3139, 10304, 38997, 140893, 570002, 2230599, 9567979, 40091222, 181203603, 805962157, 3819522284, 17912075229, 88646095447, 435959031488, 2245454002137, 11530035000169, 61627679281154
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Hankel transform is A000178.
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FORMULA
| G.f.: 1/(1-x-x^2-2x^4/(1-x-5x^2-12x^4/(1-x-9x^2-30x^4/(1-x-13x^2-56x^4/(1-.... (continued fraction);
a(n)=sum{k=0..floor(n/2), C(n-k,k)*(2k)!/(k!*2^k)}.
Conjecture: 2*a(n) -3*a(n-1) +(3-2*n)*a(n-2) +(2*n-3)*a(n-3)=0. - R. J. Mathar, Nov 14 2011
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CROSSREFS
| Sequence in context: A089790 A006785 A113182 * A006627 A077161 A068080
Adjacent sequences: A165430 A165431 A165432 * A165434 A165435 A165436
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Sep 18 2009
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