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A070740 Order of the subgroup of the symmetric group S_(2n) generated by the 2 cycles: (1,2,...n,2n,2n-1,...,n+1) and (1,2,...,2n). 1
24, 36, 40320, 7200, 479001600, 25401600, 20922789888000, 65840947200, 2432902008176640000, 1593350922240000, 620448401733239439360000, 19387894021816320000, 304888344611713860501504000000, 1710012252724199424000000, 263130836933693530167218012160000000 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
LINKS
FORMULA
If n is even: a(n) = (2n)!.
If n is congruent to 1 mod 4: a(n) = (n!)^2 / 2.
If n is congruent to 3 mod 4: a(n) = (n!)^2.
PROG
(PARI) a(n) = if(n < 2, 0, if(n%2==0, (2*n)!, (n!)^2 / if(n%4==1, 2, 1))); \\ Andrew Howroyd, Jul 04 2018
CROSSREFS
Sequence in context: A172424 A241286 A334803 * A175460 A015805 A164534
KEYWORD
nonn
AUTHOR
Sharon Sela (sharonsela(AT)hotmail.com), May 14 2002
EXTENSIONS
Terms a(8) and beyond from Andrew Howroyd, Jul 04 2018
STATUS
approved

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Last modified March 29 10:22 EDT 2024. Contains 371268 sequences. (Running on oeis4.)