OFFSET
1,1
COMMENTS
Semiprime analog of A005867.
FORMULA
a(n) = Prod[from i = 1 to n] (A001358(i)-1).
EXAMPLE
a(10) = 3*5*8*9*13*14*20*21*24*25 =
(4-1)*(6-1)*(9-1)*(10-1)*(14-1)*(15-1)*(21-1)*(22-1)*(25-1)*(26-1) = 49533120000, the product of the first 10 (semiprimes minus one).
MATHEMATICA
FoldList[Times, Select[Range[50], PrimeOmega[#]==2&]-1] (* Harvey P. Dale, Jan 21 2023 *)
PROG
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Nov 28 2005
STATUS
approved