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 A056890 Denominators of continued fraction for left factorial. 2
 1, -1, 0, -1, -2, 1, 1, 0, 1, -1, -4, 3, 14, -11, -63, 52, 353, -301, -2356, 2055, 18194, -16139, -159335, 143196, 1559017, -1415821, -16846656, 15430835, 199185034, -183754199, -2557127951, 2373373752, 35416852081, -33043478329, -526322279512, 493278801183, 8352696141782 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS G. C. Greubel, Table of n, a(n) for n = 0..900 FORMULA a(0)=1; a(1)=-1; a(2*n)=n*a(2*n-1)+a(2*n-2); a(2*n+1)= - a(2*n)+a(2*n-1) MAPLE a:= proc(n) option remember; if n<2 then (-1)^n elif (n mod 2)=0 then (n/2)*a(n-1) +a(n-2) else -a(n-1) +a(n-2) fi; end: seq(a(n), n=0..40); # G. C. Greubel, Dec 05 2019 MATHEMATICA a[n_]:= a[n]= If[n<2, (-1)^n, If[EvenQ[n], (n/2)*a[n-1] +a[n-2], -a[n-1] +a[n-2]]]; Table[a[n], {n, 0, 40}] (* G. C. Greubel, Dec 05 2019 *) PROG (PARI) a(n) = if(n<2, (-1)^n, if(Mod(n, 2)==0, (n/2)*a(n-1) +a(n-2), -a(n-1) +a(n-2) )); \\ G. C. Greubel, Dec 05 2019 (Sage) @CachedFunction def a(n): if (n<2): return (-1)^n elif (mod(n, 2) ==0): return (n/2)*a(n-1) +a(n-2) else: return -a(n-1) +a(n-2) [a(n) for n in (0..40)] # G. C. Greubel, Dec 05 2019 (GAP) a:= function(n) if n<2 then return (-1)^n; elif (n mod 2)=0 then return (n/2)*a(n-1) +a(n-2); else return -a(n-1) +a(n-2); fi; end; List([0..20], n-> a(n) ); # G. C. Greubel, Dec 05 2019 CROSSREFS Cf. A056889. Sequence in context: A294446 A318163 A114640 * A321519 A346392 A169590 Adjacent sequences: A056887 A056888 A056889 * A056891 A056892 A056893 KEYWORD sign,frac,easy AUTHOR Aleksandar Petojevic, Sep 05 2000 EXTENSIONS More terms from James A. Sellers, Sep 06 2000 and from Larry Reeves (larryr(AT)acm.org), Sep 07 2000 STATUS approved

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Last modified November 27 02:42 EST 2022. Contains 358362 sequences. (Running on oeis4.)