# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a175768 Showing 1-1 of 1 %I A175768 #27 Aug 03 2024 14:29:26 %S A175768 5,13,17,29,37,41,53,61,73,89,97,101,109,113,137,149,157,163,173,181, %T A175768 193,197,229,233,241,257,269,271,277,281,293,313,317,337,349,353,373, %U A175768 379,389,397,401,409,421,433,449,457,461,487,509,521,541,557,569,577,593,601,613 %N A175768 Primes of the form k * b^b + 1, with b > 1. %C A175768 Without the restriction on b, the sequence would be identical to A000040. %H A175768 Seiichi Manyama, Table of n, a(n) for n = 1..10000 %e A175768 For a(3), 4 * 2^2 + 1 = 17, which is prime. %e A175768 From _Seiichi Manyama_, Mar 27 2018: (Start) %e A175768 n | a(n) %e A175768 ---+---------------------------------- %e A175768 1 | 5 = 1 * 2^2 + 1. %e A175768 2 | 13 = 3 * 2^2 + 1. %e A175768 3 | 17 = 4 * 2^2 + 1. %e A175768 4 | 29 = 7 * 2^2 + 1. %e A175768 5 | 37 = 9 * 2^2 + 1. %e A175768 6 | 41 = 10 * 2^2 + 1. %e A175768 7 | 53 = 13 * 2^2 + 1. %e A175768 8 | 61 = 15 * 2^2 + 1. %e A175768 9 | 73 = 18 * 2^2 + 1. %e A175768 10 | 89 = 22 * 2^2 + 1. %e A175768 11 | 97 = 24 * 2^2 + 1. %e A175768 12 | 101 = 25 * 2^2 + 1. %e A175768 13 | 109 = 27 * 2^2 + 1 = 4 * 3^3 + 1. (End) %t A175768 Take[ Select[ Union@ Flatten@ Table[ k*b^b + 1, {b, 2, 20}, {k, 148}], PrimeQ], 55] (* _Robert G. Wilson v_, Sep 01 2010 *) %o A175768 (PARI) isA175768(n)=if(!isprime(n),return(0)); if(n%4==1||n%27==1,return(1)); forprime(b=5,log(n)/log(7),if(n%(b^b)==1,return(1)));0 \\ _Charles R Greathouse IV_, Sep 02 2010 %Y A175768 Cf. A000040, A002144, A180362, A285015. %K A175768 easy,nonn %O A175768 1,1 %A A175768 Kevin Batista (kevin762401(AT)yahoo.com), Sep 01 2010 %E A175768 Corrected and edited by _Charles R Greathouse IV_, Sep 02 2010 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE