A169818 - OEIS

%I #5 Jan 03 2013 12:39:31

%S 0,1,1,1,2,2,1,2,2,2,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,1,3,2,2,

%T 2,2,3,2,2,3,2,2,2,2,2,2,2,2,3,3,3,2,2,2,1,3,2,2,3,2,3,2,2,2,3,3,3,2,

%U 3,2,3,2,3,2,2,2,3,3,2,2,2,2,2,2,3,3,2,3,3,3,3,2,2,2,2,2,2,3,3

%N Rank of n-th prime as defined in A177854.

%C This notion of rank is closely related to the Erdős-Selfridge classification of primes.

%H T. D. Noe, <a href="/A169818/b169818.txt">Table of n, a(n) for n=1..10000</a>

%F a(A000720(A141453(n)))=1 n>1. [From _R. J. Mathar_, May 28 2010]

%t rank[1]=0; rank[2]=0; rank[3]=1;

%t SetAttributes[rank,Listable];

%t rank[p_] := rank[p] = 1+Min[Max@@rank[First/@FactorInteger[p-1]], Max@@rank[First/@FactorInteger[p+1]]]; rank[Prime[Range[100]]]

%Y For records see A177854.

%K nonn

%O 1,5

%A _T. D. Noe_, May 28 2010