The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A144717 a(n) = smallest positive integer > a(n-1) such that 2*a(1)*a(2)*...*a(n) + 1 is prime. 12
 1, 2, 3, 5, 7, 8, 9, 11, 12, 14, 17, 20, 24, 30, 34, 44, 72, 85, 86, 92, 115, 122, 125, 132, 142, 150, 161, 162, 181, 186, 198, 224, 248, 252, 282, 283, 290, 307, 319, 321, 344, 350, 376, 445, 476, 567, 623, 676, 682, 704, 741, 749, 786, 803, 806, 893, 1014, 1046 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Jon E. Schoenfield, Table of n, a(n) for n = 1..505 (lists all terms < 10^5) EXAMPLE a(1)=1 because a(0) is not defined and 2*1 + 1 = 3 is prime; a(2)=2 because 2*1*2 + 1 = 5 is prime; a(3)=3 because 2*1*2*3 + 1 = 13 is prime; a(4) is not 4 because 2*1*2*3*4 + 1 = 49 is not prime, but a(4)=5 works because 2*1*2*3*5 + 1 = 61 is prime. MATHEMATICA k = 2; a = {}; Do[If[PrimeQ[k n + 1], k = k n; AppendTo[a, n]], {n, 1, 3000}]; a (* Artur Jasinski *) nxt[{p_, a_}]:=Module[{k=a+1}, While[!PrimeQ[p*k+1], k++]; {p*k, k}]; NestList[ nxt, {2, 1}, 60][[All, 2]] (* Harvey P. Dale, Aug 18 2021 *) PROG (Python) from sympy import isprime from itertools import count, islice def agen(): # generator of terms an, p = 1, 2 while True: yield an an = next(k for k in count(an+1) if isprime(p*k+1)) p *= an print(list(islice(agen(), 58))) # Michael S. Branicky, Jan 13 2023 CROSSREFS Cf. A046966, A046972, A144718, A144722, A144723, A144724, A144725, A144726, A144727, A144728, A144729, A144730, A144731. Sequence in context: A350799 A246438 A158791 * A202728 A244016 A186042 Adjacent sequences: A144714 A144715 A144716 * A144718 A144719 A144720 KEYWORD nonn,nice AUTHOR Artur Jasinski, Sep 19 2008 EXTENSIONS Edited by N. J. A. Sloane, Sep 21 2017 following suggestions from Richard C. Schroeppel 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 May 22 11:26 EDT 2024. Contains 372745 sequences. (Running on oeis4.)