PROG
(MAGMAMagma) [1-n: n in [0..50]]; // Vincenzo Librandi, Apr 29 2011
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(MAGMAMagma) [1-n: n in [0..50]]; // Vincenzo Librandi, Apr 29 2011
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<a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
a(n) = Sum_{k=0..n} A094816(n,k)*(-1)^k (alternating row sums of Poisson-Charlier coefficient matrix).
O.g.f.: (1-2x2*x)/(1-x)^2. a(n+1) = A001489(n). -_ _R. J. Mathar_, May 28 2008
a(n) = 2*a(n-1)-a(n-2) for n>1. - Wesley Ivan Hurt, Mar 02 2016
A024000:=n->1-n: seq(A024000(n), n=0..100); # Wesley Ivan Hurt, Mar 02 2016
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Flatten[NestList[(#/.x_/; x>1->Sequence[x, 2x])-1&, {1}, 60]]
(* Robert G. Wilson v, Mar 02 2016 *)
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a(n) is the weighted sum over all derangements (permutations with no fixed points) of n elements where each permutation with an odd number of cycles has weight +1 and each with an even number of cycles has weight -1. [Michael Somos, Jan 19 2011]
a(n) is the weighted sum over all derangements (permutations with no fixed points) of n elements where each permutation with an odd number of cycles has weight +1 and each with an even number of cycles has weight -1. [From Michael Somos, Jan 19 2011]
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a(n) = 1 - n.
(MAGMA) [1-n: n in [0..50]]; // _Vincenzo Librandi, _, Apr 29 2011
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