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

1,1

Links

Table of n, a(n) for n=1..29.

Example

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.

Sequence in context: A081630 A307532 A135324 * A069688 A158323 A025119

Adjacent sequences: A107636 A107637 A107638 * A107640 A107641 A107642

Keyword

hard,more,nonn

Author

Pierre CAMI, Jun 10 2005

Status

approved