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A123026
a(n) = n!*b(n), where b(n) = ((n-1)^2 - 2)*b(n-2)/(n*(n-1)) and b(0) = b(1) = 1.
2
1, 1, -1, 2, -7, 28, -161, 952, -7567, 59024, -597793, 5784352, -71137367, 821377984, -11879940289, 159347328896, -2649226684447, 40474221539584, -760328058436289, 13032699335746048, -272957772978627751, 5187014335626927104, -119828462337617582689, 2500140909772178864128
OFFSET
0,4
LINKS
FORMULA
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
MATHEMATICA
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}]
PROG
(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;
[a(n): n in [0..30]]; // G. C. Greubel, Jul 20 2021
(Sage)
def a(n): return 1 if (n<2) else ((n-1)^2 -2)*a(n-2)
[a(n) for n in (0..30)] # G. C. Greubel, Jul 20 2021
CROSSREFS
Cf. A123025.
Sequence in context: A296726 A334613 A365559 * A013011 A013181 A191478
KEYWORD
sign
AUTHOR
Roger L. Bagula, Sep 24 2006
EXTENSIONS
Edited by N. J. A. Sloane, Oct 01 2006
Edited by G. C. Greubel, Jul 20 2021
STATUS
approved