OFFSET

1,2

COMMENTS

After 290, which may or may not be in the sequence, 420 and 450 are definitely in the sequence.

LINKS

K. O'Bryant, Sets of Natural Numbers with Proscribed Subsets, J. Int. Seq. 18 (2015) # 15.7.7

MATHEMATICA

Select[Range[200], PrimeOmega[# 23^# - 1]==2&]

PROG

(Magma) IsSemiprime:=func<i | &+[d[2]: d in Factorization(i)] eq 2>; [n: n in [2..200] | IsSemiprime(s) where s is n*23^n-1];

(PARI) isok(n)=bigomega(n*23^n-1)==2 \\ Anders HellstrÃ¶m, Aug 20 2015

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Luke March, Aug 06 2015

STATUS

approved