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A080227 a(n) = n*a(n-1) + (1/2)*(1+(-1)^n), a(0)=0. 3
0, 0, 1, 3, 13, 65, 391, 2737, 21897, 197073, 1970731, 21678041, 260136493, 3381774409, 47344841727, 710172625905, 11362762014481, 193166954246177, 3477005176431187, 66063098352192553, 1321261967043851061, 27746501307920872281, 610423028774259190183 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..450

FORMULA

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. - Gary Detlefs, Jun 22 2010

MATHEMATICA

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}]] (* Harvey P. Dale, Jul 21 2011 *)

CROSSREFS

Sequence in context: A241598 A155867 A009102 * A199143 A002468 A198663

Adjacent sequences:  A080224 A080225 A080226 * A080228 A080229 A080230

KEYWORD

easy,nonn

AUTHOR

Mario Catalani (mario.catalani(AT)unito.it), Feb 07 2003

STATUS

approved

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Last modified June 21 23:37 EDT 2021. Contains 345367 sequences. (Running on oeis4.)