A177031 Exponents n for which P#*2^n-1 is a lower twin prime, where P is the prime associated with n in A176994.

0, 1, 5, 7, 9, 12, 15, 17, 92, 130, 131, 154, 175, 189, 190, 236, 271, 290, 365, 372, 518, 558, 574, 635, 646, 748, 804, 829, 1066, 1197, 1236, 1559, 1941, 2112, 2324

Offset: 1

Author

Pierre CAMI, Dec 09 2010

Keywords

• nonn

Examples

			2*3*2^0-1=5, 2*3*2^0+1=7 twin prime of 5 so a(1)=0
2*3*2^1-1=11, 2*3*2^1+1=13 twin prime of 11 so a(2)=1
2*3*2^2-1=23 prime but not twin prime
2*3*2^3-1=47 prime but not twin prime
2*3*2^4-1=95 composite
2*3*5*2^4-1=479 prime but not twin prime
2*3*2^5-1=191, 2*3*2^5+1=193 twin prime of 191 so a(3)=5
		

Crossrefs

Cf. A001359, A034386, A176994.