A161672 Half the product of all numbers from A141468(n) up to prime(n).
0, 3, 10, 21, 3960, 77220, 490089600, 1523733120, 2075793350400, 50710801232931840000, 3144069676441774080000, 19348101737674447004467200000, 137500509682406403378413568000000
Offset: 1
Keywords
Examples
a(1)=0 is the product 0*1*2/2. a(2) is the product 1*2*3/2 = 3. a(3)=10 is the product 4*5/2.
Links
- Michael De Vlieger, Table of n, a(n) for n = 1..99
Programs
-
Mathematica
f[n_] := FixedPoint[n + PrimePi@ # &, n + PrimePi@ n]; Array[1/2*Times @@ Range[f[# - 1], Prime[#]] &, 13] (* Michael De Vlieger, Mar 22 2022, after Robert G. Wilson v at A141468 *)
Formula
a(n) = prime(n)!/ (2*(A141468(n)-1)!).
Extensions
a(0) replaced by 0 - R. J. Mathar, May 21 2010