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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: A254389 A254396 A253984 * A251372 A204852 A028965

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 December 2 23:29 EST 2016. Contains 278694 sequences.