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A169818 Rank of n-th prime as defined in A177854. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A105697 A080757 A037196 * A116543 A256911 A107260

Adjacent sequences:  A169815 A169816 A169817 * A169819 A169820 A169821

KEYWORD

nonn

AUTHOR

T. D. Noe, May 28 2010

STATUS

approved

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Last modified December 5 10:15 EST 2020. Contains 338945 sequences. (Running on oeis4.)