A048880 Primes of form pq+2 where p and q are consecutive primes.

17, 37, 79, 223, 439, 4759, 22501, 32401, 53359, 57601, 60493, 72901, 77839, 95479, 99223, 159199, 164011, 176401, 194479, 239119, 324901, 378223, 416023, 497011, 680623, 756853, 804511, 1115113, 1664101, 1742401, 2223079

Offset: 1

Author

Herman H. Rosenfeld (herm3(AT)pacbell.net)

Keywords

• easy
• nonn

Comments

All terms > 17 are congruent to 1 mod 6. - Zak Seidov, Dec 03 2010

Examples

			487*491+2=239119.
		

Links

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

Crossrefs

Cf. A051507, A123921, A342564.

Programs

Maple

with (numtheory): for n from 1 to 1000 do if (tau(ithprime(n)*ithprime(n+1)+2)=2) then print(ithprime(n),ithprime(n+1),ithprime(n)*ithprime(n+1)+2); fi; od;

Mathematica

Reap[Do[If[PrimeQ[p=Prime[k]*Prime[k+1]+2],Sow[p]],{k,1,430}]][[2,1]] (* Zak Seidov Dec 03 2010 *)

Formula

a(n) = 6*A342564(n-1) + 1 for n >= 2. - Hugo Pfoertner, Jun 24 2021

Extensions

Corrected and extended by Joe DeMaio (jdemaio(AT)kennesaw.edu).