A194635 Indices of records in A194591 restricted to prime indices.

2, 5, 13, 47, 59, 109, 241, 631, 1109, 1373, 1447, 16229, 52267, 56543, 838441, 16935761, 270704167, 3296757029

Offset

1,1

Comments

Integers for which the smallest k in A194591 such that prime(n)*2^k - 1 or prime(n)*2^k + 1 is prime (A194608) increases.

a(19) > 10^10.

A194607 gives the record values of A194606.

References

Wilfrid Keller, personal communication, 2010.

Links

Table of n, a(n) for n=1..18.

Chris K. Caldwell, The List of Largest Known Primes, 270704167 * 2^85461 - 1

Chris K. Caldwell, The List of Largest Known Primes, 3296757029 * 2^191207 + 1

Carlos Rivera, Problem 30. A stepladder to B-alpha sequence, The Prime Puzzles & Problems Connection.

Mathematica

l = -1; Flatten[Table[p = Prime[n]; k = 0; While[! PrimeQ[p*2^k - 1] && ! PrimeQ[p*2^k + 1], k++]; If[k > l, l = k; p, {}], {n, 10^4}]] (* Arkadiusz Wesolowski, Sep 04 2011 *)

Crossrefs

Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194636, A194637, A194638, A194639.

Cf. A064699, A076335, A180247, A217892.

Sequence in context: A111563 A079573 A360513 * A212821 A067021 A269068

Adjacent sequences: A194632 A194633 A194634 * A194636 A194637 A194638

Keyword

more,nonn

Author

Arkadiusz Wesolowski, Aug 31 2011

Extensions

a(17) was found in 2000 by Wilfrid Keller

a(18) was found in 2003 by Patrick De Geest

Edited by Max Alekseyev, Oct 14 2012

Edited by Arkadiusz Wesolowski, Sep 11 2013

Status

approved