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A274305
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Order of shuffle group generated by in- and out-horseshoe shuffles of a deck of 2n cards.
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1
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2, 12, 120, 32, 3628800, 95040, 87178291200, 80, 6402373705728000, 1216451004088320000, 1124000727777607680000, 310224200866619719680000, 403291461126605635584000000, 152444172305856930250752000000, 265252859812191058636308480000000, 192, 295232799039604140847618609643520000000
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OFFSET
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1,1
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LINKS
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FORMULA
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See Maple program.
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MAPLE
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f:=proc(n) local k, i, np;
if n=1 then 2
elif n=2 then 12
elif n=3 then 120
elif n=6 then 12!/7!
elif (n mod 2) = 1 then (2*n)!
else
np:=n; k:=1;
for i while (np mod 2) = 0 do
np:=np/2; k:=k+1; od;
if (n=2^(k-1)) then (k+1)*2^k else (2*n)!/2; fi;
fi;
end;
[seq(f(n), n=1..64)];
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MATHEMATICA
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a[n_] := Which[n == 1, 2, n == 2, 12, n == 3, 120, n == 6, 12!/7!, OddQ[n], (2 n)!, True, np = n; k = 1; While[EvenQ[np], np = np/2; k++]; If[n == 2^(k - 1), (k + 1)*2^k, (2n)!/2]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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