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A080227
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a(n)=na(n-1)+(1/2)(1+(-1)^n), a(0)=0.
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1
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0, 0, 1, 3, 13, 65, 391, 2737, 21897, 197073, 1970731, 21678041, 260136493, 3381774409, 47344841727, 710172625905, 11362762014481, 193166954246177, 3477005176431187, 66063098352192553, 1321261967043851061
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OFFSET
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0,4
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LINKS
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Table of n, a(n) for n=0..20.
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FORMULA
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E.g.f.:(e^x+e^(-x)-2)/(2(1-x))
a(n) = floor((cosh(1)-1)*n!) - Benoit Cloitre, Feb 14 2003
a(n) = (n-1)*(a(n-1)+a(n-2))+1, n>1 [From Gary Detlefs, Jun 22 2010]
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MATHEMATICA
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c=CoefficientList[Series[(e^x+e^(-x)-2)/(2(1-x)), {x, 0, 25}], x]; For[n = 0, n < 26, n++; Print[c[[n]]*(n - 1)! ]]
Join[{0}, RecurrenceTable[{a[1]==0, a[2]==1, a[n]==(n-1)(a[n-1]+a[n-2])+ 1}, a[n], {n, 30}]] (* From Harvey P. Dale, Jul 21 2011 *)
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CROSSREFS
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Sequence in context: A141342 A155867 A009102 * A199143 A002468 A198663
Adjacent sequences: A080224 A080225 A080226 * A080228 A080229 A080230
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KEYWORD
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easy,nonn
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Feb 07 2003
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STATUS
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approved
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