A194639 - OEIS

A194639

Indices of records in A194591 when it is restricted to odd indices.

1, 5, 13, 47, 59, 109, 241, 335, 1109, 1373, 1447, 14893, 52267, 56543, 649603, 838441, 8840101, 16935761, 100604513, 118373279, 270704167, 1355477231

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OFFSET

1,2

COMMENTS

Integers for which the smallest k in A194591 such that (2*n-1)*2^k - 1 or (2*n-1)*2^k + 1 is prime (A194638) increases.

A194637 gives the record values of A194636.

REFERENCES

Wilfrid Keller, personal communication, 2010.

LINKS

Table of n, a(n) for n=1..22.

Chris K. Caldwell, The List of Largest Known Primes, 1355477231 * 2^356981 + 1

Carlos Rivera, Problem 30

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, {}], {n, 10^5}]] (* Arkadiusz Wesolowski, Sep 04 2011 *)

CROSSREFS

Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194637, A194638.

Cf. A064699, A076335, A180247, A217892.

Cf. A217892 (indices of records of unrestricted A194591)

Sequence in context: A099972 A060050 A217892 * A152925 A304964 A120790

Adjacent sequences: A194636 A194637 A194638 * A194640 A194641 A194642

KEYWORD

more,nonn

AUTHOR

Arkadiusz Wesolowski, Aug 31 2011

EXTENSIONS

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

Definition corrected by Max Alekseyev and Farideh Firoozbakht, Oct 16 2014

STATUS

approved