A177215 Numbers k that are the products of two distinct primes such that 2*k-1, 4*k-3, 8*k-7, 16*k-15, 32*k-31 and 64*k-63 are also products of two distinct primes.

694, 3403, 4714, 5062, 5353, 7495, 11293, 12139, 13798, 14191, 19735, 21439, 22585, 24277, 25009, 25399, 26734, 26899, 31261, 32959, 35299, 36199, 44869, 48949, 49471, 50797, 58003, 60181, 62521, 70759, 72397, 73909, 75631, 79021, 83086

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 04 2010

Keywords

• nonn

Examples

			694 is a term because 694 = 2*347, 2*694 - 1 = 1387 = 19*73, 4*694 - 1 = 2773 = 47*59, 8*694 - 1 = 5545 = 5*1109, 16*694 - 1 = 11089 = 13*853, 32*694 - 1 = 22177 = 67*331, and 64*694 - 1 = 44353 = 17*3609.
		

Crossrefs

Cf. A006881, A177210, A177211, A177212, A177213, A177214.

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1}; lst={};Do[If[f[n]&&f[2*n-1]&&f[4*n-3]&&f[8*n-7]&&f[16*n-15]&&f[32*n-31]&&f[64*n-63],AppendTo[lst,n]],{n,0,9!}];lst