A094261 a(n) = n(n-1)(n-3)(n-6)...(n-t), where t is the largest triangular number less than n; number of factors in the product is ceiling((sqrt(1+8*n)-1)/2).

1, 2, 6, 12, 40, 90, 168, 560, 1296, 2520, 4400, 14256, 32760, 64064, 113400, 187200, 586432, 1321920, 2560896, 4522000, 7484400, 11797632, 35784320, 78871968, 150480000, 263120000, 433060992, 681080400, 1033305728, 3044304000

Offset

1,2

Links

Table of n, a(n) for n=1..30.

Example

a(8) = 8*(8-1)*(8-3)*(8-6) = 8*7*5*2 = 560.

Maple

a:=n->product(n-k*(k+1)/2, k=0..ceil((sqrt(1+8*n)-1)/2)-1): seq(a(n), n=1..35); # Emeric Deutsch, Feb 03 2006

Crossrefs

Cf. A057944, A094262.

Sequence in context: A123045 A280171 A327879 * A080497 A127724 A178008

Adjacent sequences: A094258 A094259 A094260 * A094262 A094263 A094264

Keyword

nonn

Author

Amarnath Murthy, Apr 26 2004

Extensions

Corrected and extended by Emeric Deutsch, Feb 03 2006

Status

approved