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A081641 a(n) = n-th prime of class 13- according to the Erdős-Selfridge classification. 6
36449279, 53065907, 59681213, 69096887, 132756479, 135388367, 164255999, 179043637, 188991053, 207290663, 241560239, 279709259, 309550999, 364492781, 372993983, 377982103, 398007431, 406165099, 425633717, 445901987, 447609067, 516737983 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, A18.

LINKS

M. F. Hasler, Table of n, a(n) for n=1..1641

MATHEMATICA

PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]]; f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], m /= 2]; While[ IntegerQ[m/3], m /= 3]]; Apply[Times, PrimeFactors[m] - 1]]; ClassMinusNbr[n_] := Length[ NestWhileList[f, n, UnsameQ, All]] - 3; Prime[ Select[ Range[23733333], ClassMinusNbr[ Prime[ # ]] == 12 &]]

PROG

(PARI) A081641 = nextclassminus(A081640) /* cf. A081640 */ - M. F. Hasler, Apr 05 2007

CROSSREFS

Cf. A005113, A005105, A005106, A005107, A005108, A081633, A081633, A081635, A081636, A081637, A081638.

Cf. A056637, A081640, A129248.

Sequence in context: A183593 A183755 A105296 * A204852 A028965 A215130

Adjacent sequences:  A081638 A081639 A081640 * A081642 A081643 A081644

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Mar 23 2003

EXTENSIONS

Edited by N. J. A. Sloane, May 14 2008 at the suggestion of R. J. Mathar.

STATUS

approved

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Last modified October 25 02:31 EDT 2014. Contains 248517 sequences.