A107639 Smallest prime a such that (a*b)^2 + a*b -1 is prime with b prime = 2^(2*n) - 2^n - 1, see A098845 for n.

5, 7, 31, 11, 5, 3, 809, 661, 139, 73, 521, 701, 131, 487, 89, 211, 733, 3011, 311, 8837, 2837, 8831, 1733, 401, 983, 17881, 1783, 19553, 13859

Offset: 1

Author

Pierre CAMI, Jun 10 2005

Keywords

• hard
• more
• nonn

Examples

			2^4-2^2-1=3=b(1) prime, (3*3)^2+3*3-1=89 prime so a(1)=3
2^8-2^4-1=239=b(2) prime, (7*239)^2+7*239-1=2800601 prime so a(2)=7
		

Crossrefs

Cf. A098845.