OFFSET
1,1
COMMENTS
EXAMPLE
The unique prime factor sets are {3} (m=2), {2} (m=3), {5,7} (m=6), {3,7} (m=8), {2,5} (m=9) etc.
MATHEMATICA
aa = {}; bb = {}; cc = {}; ff = {}; Do[k = n^2 - 1; kk = FactorInteger[k]; b = {}; Do[AppendTo[b, kk[[m]][[1]]], {m, 1, Length[kk]}]; dd = Position[aa, b]; If[dd == {}, AppendTo[cc, n]; AppendTo[aa, b], AppendTo[ff, n]; AppendTo[bb, cc[[dd[[1]][[1]]]]]], {n, 2, 1000000}]; jj=Table[n, {2, 99}]; ss=Union[bb, ff]; Take[Complement[jj, ss], 63] (*Artur Jasinski*)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Oct 12 2010, Oct 21 2010
STATUS
approved