The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A093481 Least k such that (2n + k) + 1 and (2n*k) + 1 are both primes. 2
 2, 18, 6, 2, 6, 6, 2, 6, 4, 2, 18, 4, 2, 12, 6, 8, 12, 16, 20, 6, 10, 2, 6, 4, 2, 6, 24, 2, 30, 10, 26, 18, 6, 2, 36, 6, 8, 6, 4, 8, 66, 4, 2, 24, 6, 14, 12, 6, 2, 6, 4, 32, 30, 4, 26, 18, 34, 50, 30, 10, 8, 12, 52, 2, 18, 16, 2, 60, 10, 32, 6, 4, 2, 30, 12, 14, 24, 6, 14, 30, 10, 14, 6, 4, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n>1 a(n) is even and also if a(n) = m then a(m/2) = 2n. LINKS EXAMPLE a(4) = 2, 8 + 2 + 1 = 11 and 8*2 + 1 = 17 are both prime. MATHEMATICA f[n_] := Block[{k = 1}, While[ !PrimeQ[2n + k + 1] || ! PrimeQ[2n*k + 1], k++ ]; k]; Table[ f[n], {n, 85}] (* Robert G. Wilson v, Apr 24 2004 *) CROSSREFS Twice A093312. Sequence in context: A094048 A179073 A087665 * A132629 A288161 A302454 Adjacent sequences:  A093478 A093479 A093480 * A093482 A093483 A093484 KEYWORD nonn AUTHOR Amarnath Murthy, Apr 14 2004 EXTENSIONS Edited, corrected and extended by Robert G. Wilson v, Apr 24 2004 STATUS approved

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

Last modified December 5 00:21 EST 2021. Contains 349530 sequences. (Running on oeis4.)