The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A194608 Smallest prime either of the form prime(n)*2^k - 1 or prime(n)*2^k + 1, k >= 0, or 0 if no such prime exists, where prime(n) denotes the n-th prime number. 13
 3, 2, 11, 13, 23, 53, 67, 37, 47, 59, 61, 73, 83, 173, 751, 107, 1889, 487, 269, 283, 293, 157, 167, 179, 193, 809, 823, 857, 6977, 227, 509, 263, 547, 277, 1193, 2417, 313, 653, 2671, 347, 359, 1447, 383, 773, 787, 397, 421, 1783, 907, 457, 467, 479, 493567 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes arising from A194606 (or 0 if no such prime exists). LINKS Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1000 EXAMPLE For n=4, 7*2^0-1 and 7*2^0+1 are composite, but 7*2^1-1=13 is prime, so a(4)=13. MATHEMATICA Table[p = Prime[n]; k = 0; While[! PrimeQ[a = p*2^k - 1] && ! PrimeQ[a = p*2^k + 1], k++]; a, {n, 100}] (* Arkadiusz Wesolowski, Sep 04 2011 *) CROSSREFS Cf. A194591, A194600, A194603, A194606, A194607, A194635, A194636, A194637, A194638, A194639. Cf. A038699, A050921, A076335, A180247. Sequence in context: A074246 A134426 A122672 * A297870 A052973 A087956 Adjacent sequences: A194605 A194606 A194607 * A194609 A194610 A194611 KEYWORD nonn AUTHOR Arkadiusz Wesolowski, Aug 30 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 23 07:16 EDT 2024. Contains 371905 sequences. (Running on oeis4.)