A194637 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

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.

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

FORMULA

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

EXAMPLE

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

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 *)

CROSSREFS

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

Cf. A103963, A103964, A076335, A180247.

Sequence in context: A101951 A171166 A194607 * A194600 A255543 A256458

Adjacent sequences: A194634 A194635 A194636 * A194638 A194639 A194640

KEYWORD

more,nonn

AUTHOR

Arkadiusz Wesolowski, Aug 31 2011

EXTENSIONS

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

STATUS

approved