A143357 Floor((n-1)!/[n(n+1)]).

0, 0, 0, 0, 0, 2, 12, 70, 448, 3298, 27490, 255876, 2631876, 29652480, 363242880, 4807626352, 68375130352, 1040021719578, 16848351857178, 289631191449600, 5266021662720000, 100970241446066086, 2036233202495666086, 43086694564808294400, 954536002666522214400, 22095740802465792000000

Offset

1,6

Comments

All terms are even.

References

T. Andreescu, D. Andrica and Z. Feng, 104 Number Theory Problems (from the training of the USA IMO team), Birkhäuser, Boston, 2007, Introductory problem # 50, pp. 82,126,127.

Links

Table of n, a(n) for n=1..26.

Maple

seq(floor(factorial(n-1)/(n*(n+1))), n=1..25);

Mathematica

Table[Floor[(n-1)!/(n(n+1))], {n, 30}] (* Harvey P. Dale, Apr 11 2012 *)

Crossrefs

Sequence in context: A001542 A059229 A001251 * A357831 A012426 A012421

Adjacent sequences: A143354 A143355 A143356 * A143358 A143359 A143360

Keyword

nonn

Author

Emeric Deutsch, Aug 11 2008

Status

approved