A194637 Record values in A194636.

0, 1, 2, 4, 5, 6, 11, 18, 20, 28, 70, 106, 150, 726, 2906, 7431, 14073, 22394, 41422, 82587, 85461, 356981

Offset: 1

Author

Arkadiusz Wesolowski, Aug 31 2011

Keywords

• more
• nonn

Comments

The index sequence is 1, 3, 7, 24, 30, 55, 121, 168, 555, 687, 724, 7447, 26134, 28272, 324802, 419221, 4420051, 8467881, 50302257, 59186640, 135352084, 677738616, ... given by formula (A194639(n)+1)/2.

Examples

			A194636(55) = 6 since A194636(121) = 11 is the next record value.
		

References

• Wilfrid Keller, personal communication, 2010.

Links

• Chris K. Caldwell, The List of Largest Known Primes, 1355477231 * 2^356981 + 1
• Carlos Rivera, Problem 30

Crossrefs

Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194638, A194639.

Cf. A103963, A103964, A076335, A180247.

Programs

Mathematica

l = -1; Flatten[Table[n = 2*n - 1; k = 0; While[! PrimeQ[n*2^k - 1] && ! PrimeQ[n*2^k + 1], k++]; If[k > l, l = k, {}], {n, 10^5}]] (* Arkadiusz Wesolowski, Sep 04 2011 *)

Formula

a(n) = A194591(A194639(n)) = A194636((A194639(n)+1)/2).

Extensions

a(22) was found in 2002 by Wilfrid Keller.