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Search: id:A089626
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| A089626 |
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a(n) = 1/h(n) where {h(n)} is the Hankel transform of {t(n)}; t(n) is defined by the expansion of tan(x)= Sum_n>0, t(n)*x^(2*n-1); |x|<Pi/2. |
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1
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| 1, 45, 4465125, 6272287562165625, 438120013555654794702228515625, 3943988517696329309474874414036059896739501953125, 9860368980530253649041813027973243717504383071655695011832599639892578125
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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t(n)= (2^(2*n)-1)*2^(2*n)*B_n /(2*n)! B_n: numbers of Bernoulli, sequence 1/6, 1/30, 1/42, 1/30, 5/66, ... example:n=2, a(2)= 1/det|1, 1/3|1/3, 2/15|= 1/(1/45)=45 See A001906 for the definition of Hankel transform.
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FORMULA
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a(n) = (4*n-3)^1*(4*n-5)^2*...*3^(2*n-2)*1^(2*n-1).
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CROSSREFS
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Cf.
Sequence in context: A007537 A125113 A003739 this_sequence A110479 A023934 A022076
Adjacent sequences: A089623 A089624 A089625 this_sequence A089627 A089628 A089629
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KEYWORD
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easy,nonn
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AUTHOR
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DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Dec 31 2003
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