A169818 Rank of n-th prime as defined in A177854.

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, 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, 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

Offset

1,5

Comments

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

Links

T. D. Noe, Table of n, a(n) for n=1..10000

Formula

a(A000720(A141453(n)))=1 n>1. [From R. J. Mathar, May 28 2010]

Mathematica

rank[1]=0; rank[2]=0; rank[3]=1;
SetAttributes[rank, Listable];
rank[p_] := rank[p] = 1+Min[Max@@rank[First/@FactorInteger[p-1]], Max@@rank[First/@FactorInteger[p+1]]]; rank[Prime[Range[100]]]

Crossrefs

For records see A177854.

Sequence in context: A080757 A037196 A368594 * A367816 A116543 A256911

Adjacent sequences: A169815 A169816 A169817 * A169819 A169820 A169821

Keyword

nonn

Author

T. D. Noe, May 28 2010

Status

approved