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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
OFFSET
1,5
COMMENTS
This notion of rank is closely related to the Erdős-Selfridge classification of primes.
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
KEYWORD
nonn
AUTHOR
T. D. Noe, May 28 2010
STATUS
approved