A177211 Numbers k that are the products of two distinct primes such that 2*k-1 and 4*k-3 are also products of two distinct primes.

33, 118, 119, 134, 146, 226, 247, 249, 287, 295, 334, 335, 386, 391, 393, 395, 422, 478, 493, 497, 502, 519, 551, 583, 589, 614, 629, 634, 694, 697, 721, 731, 749, 755, 789, 802, 817, 843, 879, 898, 955, 958, 985, 989, 1003, 1037, 1079, 1114, 1154, 1159, 1177

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 04 2010

Keywords

• nonn

Examples

			33 is a term because 33 = 3*11, 2*33 - 1 = 65 = 5*13 and 2*65 - 1 = 4*33 - 3 = 129 = 3*43.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A006881, A177210

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1}; lst={};Do[If[f[n]&&f[2*n-1]&&f[4*n-3],AppendTo[lst,n]],{n,0,7!}];lst
tdpQ[n_]:=PrimeNu[n]==PrimeOmega[n]==PrimeNu[2n-1]==PrimeOmega[2n-1] == PrimeNu[4n-3]==PrimeOmega[4n-3]==2; Select[Range[1200],tdpQ] (* Harvey P. Dale, Nov 15 2020 *)

Extensions

Definition clarified by Harvey P. Dale, Nov 15 2020