A217195 Primes p such that p-2 is the greatest semiprime less than p.

17, 37, 41, 53, 67, 71, 79, 89, 97, 113, 131, 157, 163, 211, 223, 239, 251, 269, 293, 307, 311, 331, 337, 367, 373, 379, 397, 409, 419, 439, 449, 487, 491, 499, 521, 547, 593, 599, 613, 631, 673, 683, 691, 701, 709, 733, 739, 751, 757, 769, 773, 787, 809

Offset: 1

Author

Antonio Roldán, Sep 27 2012

Keywords

• nonn

Comments

This is a subsequence of A063638.

Examples

			487 is prime, 486 = 2*3^5 is not semiprime and 485 = 5*97 is semiprime.
		

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000

Programs

Mathematica

SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Prime[Range[200]], ! SemiPrimeQ[# - 1] && SemiPrimeQ[# - 2] &] (* T. D. Noe, Sep 27 2012 *)

PARI

forprime(p=3, 9999, bigomega(p-2)==2 && bigomega(p-1)!=2 & print1(p", "))