A052334 Record primes reached in A052333.

3, 5, 7, 19, 31, 43, 103, 223, 367, 463, 5503, 738197503

Offset: 1

Author

Christian G. Bower, Dec 19 1999

Keywords

• nonn
• nice

Comments

Start with n=1, take 2n+1, if composite take 2n+1 again, keep going until you reach a prime. Repeat for n=2, 3... If prime is a record, add to sequence. If never reach a prime, skip that value of n.

a(13) is a 771-digit prime reached after 2552 iterations starting from 73. - Warut Roonguthai. This was proved to be a prime by Paul Jobling (Paul.Jobling(AT)WhiteCross.com) using PrimeForm and by Ignacio Larrosa Cañestro using Titanix (http://www.znz.freesurf.fr/pages/titanix.html). [Oct 30 2000]

Links

• Amiram Eldar, Table of n, a(n) for n = 1..13

Crossrefs

Cf. A050412, A051914, A052333, A052339, A052340.

Programs

Mathematica

record = 2; Reap[For[n = 1, n <= 100, n++, k = n; While[ !PrimeQ[k = 2*k + 1]]; If[k > record, Print[k]; Sow[k]; record = k]]][[2, 1]] (* Jean-François Alcover, Jul 19 2013 *)

Formula

a(n) = A052333(A051914(n)). - Amiram Eldar, Jul 25 2019