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
CROSSREFS
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