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A123026
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a(n) = n!*b(n), where b(n) = ((n-1)^2 - 2)*b(n-2)/(n*(n-1)) and b(0) = b(1) = 1.
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2
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1, 1, -1, 2, -7, 28, -161, 952, -7567, 59024, -597793, 5784352, -71137367, 821377984, -11879940289, 159347328896, -2649226684447, 40474221539584, -760328058436289, 13032699335746048, -272957772978627751, 5187014335626927104, -119828462337617582689, 2500140909772178864128
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) = n!*b(n), where b(n) = (n^2 - 2*n - 1)*b(n) and b(0) = b(1) = 1.
a(n) = ((n-1)^2 - 2)*a(n-2) with a(0) = a(1) = 1. - G. C. Greubel, Jul 20 2021
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MATHEMATICA
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b[n_]:= b[n]= If[n<2, 1, ((n-1)^2 -2)*b[n-2]/(n*(n-1))];
Table[b[n]*n!, {n, 0, 30}]
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PROG
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(Magma)
function a(n)
if n lt 2 then return 1;
else return ((n-1)^2 -2)*a(n-2);
end if; return a;
end function;
(Sage)
def a(n): return 1 if (n<2) else ((n-1)^2 -2)*a(n-2)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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