A134622 Products pq ("semiprimes") of two primes p and q >= p such that q+2 is a prime.

6, 9, 10, 15, 22, 25, 33, 34, 51, 55, 58, 77, 82, 85, 87, 118, 119, 121, 123, 142, 145, 177, 187, 202, 203, 205, 213, 214, 221, 274, 287, 289, 295, 298, 303, 319, 321, 355, 358, 377, 382, 394, 411, 413, 447, 451, 454, 478, 493, 497, 505, 533, 535, 537, 538, 551, 562, 573

Offset: 1

Author

N. J. A. Sloane, Oct 17 2009

Keywords

• nonn

Crossrefs

Cf. A108605.

Programs

Maple

p:=ithprime;
t1:=[];
for i from 1 to 100 do
p1:=p(i);
for j from i to 100 do
p2:=p(j);
if isprime(p2+2) then t1:=[op(t1),p1*p2]; fi;
od: od:
t2:=sort(t1);

Mathematica

Select[Range[573],PrimeOmega[#]==2&&PrimeQ[Divisors[#][[-2]]+2]&] (* James C. McMahon, Apr 08 2025 *)