The OEIS is supported by the many generous donors to the OEIS 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 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A089727 Largest prime of the form n*k+1, k <= n. 3
 2, 5, 7, 17, 11, 37, 43, 41, 73, 101, 89, 109, 157, 197, 211, 257, 239, 307, 229, 401, 421, 463, 461, 577, 601, 677, 541, 757, 523, 811, 683, 929, 991, 1123, 1051, 1297, 1259, 1217, 1483, 1601, 1559, 1723, 1721, 1453, 1801, 1979, 2069, 2161, 1667, 2351, 2551 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE a(5)=11 because 5*2+1=11 is prime, whereas 5*5+1=26, 5*4+1=21 and 5*3+1=16 are composite. MATHEMATICA f[n_] := Block[{k = n}, While[ !PrimeQ[k*n + 1], k-- ]; k*n + 1]; Array[f, 51] (* Robert G. Wilson v, Dec 17 2009 *) PROG (PARI) A089727(n) = {local(k); k=n; while(!isprime(n*k+1), k--); n*k+1} \\ Michael B. Porter, Dec 17 2009 CROSSREFS Cf. A089726. Sequence in context: A082088 A075881 A208241 * A113514 A145674 A067161 Adjacent sequences: A089724 A089725 A089726 * A089728 A089729 A089730 KEYWORD nonn,easy AUTHOR Amarnath Murthy, Nov 18 2003 EXTENSIONS More terms from Hugo Pfoertner, Apr 01 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 5 02:30 EST 2022. Contains 358572 sequences. (Running on oeis4.)