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A142722
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a(0)=a(1)=1 and a(n) = -(2*n-1)*a(n-1) + a(n-2) for n>=2.
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0
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1, 1, -2, 11, -79, 722, -8021, 104995, -1582946, 27015077, -514869409, 10839272666, -249818140727, 6256292790841, -169169723493434, 4912178274100427, -152446696220606671, 5035653153554120570, -176400307070614826621, 6531847014766302705547
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OFFSET
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0,3
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LINKS
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Table of n, a(n) for n=0..19.
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MAPLE
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a:= proc(n) if n<2 then 1 else a(n) := -(2*n-1)*a(n-1) + a(n-2) fi end:
seq (a(n), n=0..25); # Sergei N. Gladkovskii, Jul 04 2012
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MATHEMATICA
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k = 2; b[0] = 1; b[n_] := b[n] = b[n - 1] + k
M[0] := {{-b[n], -1}, {1, 0}};
M[1] := {{-b[n], 1}, {-1, 0}};
v[0] = {1, 1};
v[n_] := v[n] = M[Mod[n, 2]].v[n - 1];
Table[v[n][[1]], {n, 1, 30}]
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PROG
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(PARI)
a(n)= if ( n<=1, 1, -(2*n-1)*a(n-1) + a(n-2) );
/* note this is inefficient, optimize using memoization: */
v=vector(66); v[1]=1; v[2]=1; /* PARI's vectors are one-based */
for (n=3, #v, v[n] = -(2*n-3)*v[n-1] + v[n-2]);
v /* show terms */
/* Joerg Arndt, Jul 023 2012 */
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CROSSREFS
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Sequence in context: A151418 A154273 A163203 * A099661 A027110 A118969
Adjacent sequences: A142719 A142720 A142721 * A142723 A142724 A142725
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KEYWORD
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sign
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AUTHOR
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Roger L. Bagula and Gary W. Adamson, Sep 27 2008
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STATUS
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approved
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