login
Least prime of level 2n-1 (cf. A117563).
0

%I #7 Jul 15 2012 09:11:10

%S 5,11,17,509,29,83,41,79,887,59,109,71,331,193,383,190717,101,107,787,

%T 277,1129,911,137,1181,149,463,1013,839,1087,179,433,191,197,4093,349,

%U 503,2423,227,701,239,5378731,587,601,439,269,6491,281,1621,877,499

%N Least prime of level 2n-1 (cf. A117563).

%F Levels of primes are defined in A117563. Conjecture: there are an infinite number of prime members at each level.

%e The first occurrence of 1 in A117563 is a(3) which implies the third prime which is 5.

%e The first occurrence of 3 in A117562 is a(5) which implies the fifth prime which is 11.

%e The first occurrence of 5 in A117562 is a(7) which implies the seventh prime which is 17, etc.

%t f[n_] := If[n == 1, 0, Block[{p = Prime@n, np = Prime[n + 1]}, (2p - np)/Min@Select[Divisors[2p - np], # >= np - p &]]]; t = Table[0, {100}]; Do[a = (f@n + 1)/2; If[a < 101 && t[[a]] == 0, t[[a]] = Prime@n; Print[{a, n, Prime@n}]], {n, 10^6}]

%Y Cf. A117078, A117563, A117873, A117874, A118481, A118508.

%K nonn

%O 1,1

%A _RĂ©mi Eismann_ and _Robert G. Wilson v_, May 12 2006