A224795 - OEIS

%I #5 Apr 21 2013 14:54:05

%S 7,17,3,5,3,61,7,5,3,5,11,37,0,53,3,5,3,13,7,5,7,37,3,13,7,5,3,193,3,

%T 13,19,29,3,5,11,109,19,5,3,5,131,109,11,5,3,5,3,61,23,5,7,13,3,13,7,

%U 29,3,29,3,73,7,0,331,5,3,61,7,5,3,53,59,13,11,5,3

%N Smallest prime q such that 2n+1 = 2p - q^3 for some odd prime p, or 0 if no such prime exists.

%C See the conjecture and the comments in A224794, and the corresponding primes p.

%H Michel Lagneau, <a href="/A224795/b224795.txt">Table of n, a(n) for n = 1..10000</a>

%e a(4) = 5 because, for (p, q) = (67, 5),  2*4+1 = 9 = 2*67 - 5^3 = 134 - 125 = 9.

%p for n from 3 by 2 to 200 do:jj:=0:for j from 1 to 50000 while (jj=0) do:q:=ithprime(j):p:=(q^3+n)/2:if type(p,prime)=true  then jj:=1: printf(`%d, `,q):else fi:od:if jj=0 then printf(`%d, `,0):else fi:od:

%Y Cf. A224730, A185046, A224794.

%K nonn

%O 1,1

%A _Michel Lagneau_, Apr 18 2013