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
Keywords
Examples
a(8) = 8*(8-1)*(8-3)*(8-6) = 8*7*5*2 = 560.
Programs
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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
Extensions
Corrected and extended by Emeric Deutsch, Feb 03 2006