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 A286032 a(n) = a(n-1) - n*a(n-2); a(0) = a(1) = 1. 1
 1, 1, -1, -4, 0, 20, 20, -120, -280, 800, 3600, -5200, -48400, 19200, 696800, 408800, -10740000, -17689600, 175630400, 511732800, -3000875200, -13747264000, 52271990400, 368459062400, -886068707200, -10097545267200, 12940241120000, 285573963334400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Indranil Ghosh, Table of n, a(n) for n = 0..500 FORMULA a(n) = n! [x^n] (1 - sqrt(Pi / 2) * exp(-((x - 1)^2) / 2) * (x - 1) * (erfi((x - 1) / sqrt(2)) + erfi(1 / sqrt(2)))). Generating function satisfies x^3*A'(x) + (2*x^2-x+1)*A(x) = 1. MAPLE a := proc(n) option remember; if n <= 1 then 1 else a(n-1) - n*a(n-2) fi end: seq(a(n), n = 0..27); a_list := proc(len) 1 - sqrt(Pi/2)*exp(-((x-1)^2)/2)*(x-1)* (erfi((x-1)/sqrt(2)) + erfi(1/sqrt(2))); series(%, x, len+2): seq(n!*simplify(coeff(%, x, n)), n=0..len-1) end: a_list(27); MATHEMATICA l={1, 1}; Do[AppendTo[l, l[[-1]] - n*l[[-2]]], {n, 2, 30}]; l (* Indranil Ghosh, May 01 2017 *) RecurrenceTable[{a[0]==a[1]==1, a[n]==a[n-1]-n a[n-2]}, a, {n, 40}] (* Harvey P. Dale, Jun 20 2021 *) PROG (Python) l=[1, 1] a=b=1 i=2 while i<=30:     l.append(b - i*a)     b=l[-1]     a=l[-2]     i+=1 print(l) # Indranil Ghosh, May 01 2017 CROSSREFS Row sums of A137286. Sequence in context: A283012 A284136 A284178 * A199933 A078630 A178671 Adjacent sequences:  A286029 A286030 A286031 * A286033 A286034 A286035 KEYWORD sign AUTHOR Peter Luschny, May 01 2017 STATUS approved

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Last modified August 4 15:33 EDT 2021. Contains 346447 sequences. (Running on oeis4.)