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A081641
a(n) = n-th prime of class 13- according to the Erdős-Selfridge classification.
4
36449279, 53065907, 59681213, 69096887, 132756479, 135388367, 164255999, 179043637, 188991053, 207290663, 241560239, 279709259, 309550999, 364492781, 372993983, 377982103, 398007431, 406165099, 425633717, 445901987, 447609067, 516737983
OFFSET
1,1
REFERENCES
R. K. Guy, Unsolved Problems in Number Theory, A18.
LINKS
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
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