OFFSET
1,1
LINKS
Zak Seidov, Table of n, a(n) for n = 1..2000
EXAMPLE
MATHEMATICA
f = Flatten@Position[Differences@(s = Select[Range@100000, PrimeOmega@# == 2 &]), 20]; s[[f]] (* Hans Rudolf Widmer, Aug 19 2024 *)
PROG
(Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [n: n in [4..130000] | IsSemiprime(n) and IsSemiprime(n+20) and forall{n+i: i in [1..19] | not IsSemiprime(n+i)}]; // Bruno Berselli, Oct 01 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Oct 01 2012
STATUS
approved