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 A050921 Smallest prime of form n*2^m+1, m >= 0, or 0 if no prime exists. 12
 2, 3, 7, 5, 11, 7, 29, 17, 19, 11, 23, 13, 53, 29, 31, 17, 137, 19, 1217, 41, 43, 23, 47, 97, 101, 53, 109, 29, 59, 31, 7937, 257, 67, 137, 71, 37, 149, 1217, 79, 41, 83, 43, 173, 89, 181, 47 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes arising from A040076 (or 0 if no such prime exists). Or: Starting with x=n+1, the first prime created by iterating the map x-> 2*x-1. - Kevin L. Schwartz and Christian N. K. Anderson, May 13 2013 LINKS R. J. Mathar, Table of n, a(n) for n = 1..382 MAPLE A050921 := proc(n)     for m from 0 do         if isprime(n*2^m+1) then             return n*2^m+1 ;         end if;     end do; end proc; # R. J. Mathar, Jun 01 2013 MATHEMATICA Do[m = 0; While[ !PrimeQ[n*2^m + 1], m++ ]; Print[n*2^m + 1], {n, 1, 47} ] CROSSREFS Cf. A040076, A034694, A038699. Sequence in context: A241082 A219789 A034694 * A087386 A110359 A092977 Adjacent sequences:  A050918 A050919 A050920 * A050922 A050923 A050924 KEYWORD nonn,easy,nice AUTHOR N. J. A. Sloane, Dec 30 1999 EXTENSIONS The next term (47*2^583 + 1) is too large to show. STATUS approved

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Last modified May 18 22:26 EDT 2021. Contains 344004 sequences. (Running on oeis4.)