OFFSET
1,2
COMMENTS
a(39+k) > 9594, for any k >= 1. It is getting much harder for n>39. It took the Mathematica program weeks to get the first 39 items.
EXAMPLE
MATHEMATICA
b = 2; max = 39; Array[fa, max]; Do[
fa[k] = 0, {k, 1, max}]; filled = 0; i = 0; While[filled < max, i++;
c1 = b^i; cs = {};
Do[c2 = b^j; cp = c1 + c2 + 1; If[PrimeQ[cp], cs = Union[cs, {cp}]];
cp = c1 + c2 - 1; If[PrimeQ[cp], cs = Union[cs, {cp}]];
cp = c1 - c2 + 1; If[PrimeQ[cp], cs = Union[cs, {cp}]];
cp = c1 - c2 - 1;
If[PrimeQ[cp], cs = Union[cs, {cp}]], {j, 0, i - 1}];
ct = Length[cs];
If[ct <= max, If[fa[ct] == 0, fa[ct] = i; filled++]]]; Table[
fa[k], {k, 1, max}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Lei Zhou, Oct 06 2011
STATUS
approved