A122581 a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3) - 4*a(n - 4) + 2*a(n - 5).
1, 1, 1, 1, 1, -2, -5, -2, 4, 13, 19, -5, -50, -65, -20, 118, 283, 187, -311, -914, -1001, 334, 3040, 4405, 835, -8273, -17030, -11189, 20068, 60178, 60427, -29165, -192491, -274310, -39845, 553798, 1070812, 635629, -1341437, -3836765, -3693914, 2237287, 12425356, 16921054, 1409755, -36343973
Offset: 1
Keywords
Links
- G. C. Greubel, Table of n, a(n) for n = 1..1000
- Index entries for linear recurrences with constant coefficients, signature (1,-2,1,-4,2).
Programs
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Maple
A122581:= proc(n) option remember; if n <= 5 then 1; else A122581(n-1) -2*A122581(n-2)+A122581(n-3)+2*(-2*A122581(n-4)+A122581(n-5)); fi; end: seq(A122581(n),n=1..50) ; # R. J. Mathar, Sep 18 2007
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Mathematica
a[n_]:= a[n]= If[n<6, 1, a[n-1] -2*a[n-2] +a[n-3] -2*(2*a[n-4] -a[n-5])]; Table[a[n], {n,50}] -
Sage
@CachedFunction # a=A122581 def a(n): return 1 if (n<6) else a(n-1) -2*a(n-2) +a(n-3) -4*a(n-4) +2*a(n-5) [a(n) for n in (1..50)] # G. C. Greubel, Nov 28 2021
Formula
G.f.: x*(1+2*x^2+x^3+5*x^4)/(1-x+2*x^2-x^3+4*x^4-2*x^5). - R. J. Mathar, Nov 18 2007
Extensions
Edited by N. J. A. Sloane, Oct 01 2006
More terms from R. J. Mathar, Sep 18 2007
Comments