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A144851
a(n) = number of distinct prime divisors (taken together) of numbers of the form 2x^2+1 for x<=10^n.
4
8, 76, 760, 7445, 73477, 726948, 7218256, 71801859, 715087632, 7127665635, 71089166879, 709344259821
OFFSET
1,1
MATHEMATICA
d = 10; l = 0; p = 2; c = {}; a = {}; Do[k = p x^2 + 1; b = Divisors[k]; Do[If[PrimeQ[b[[n]]], AppendTo[a, b[[n]]]], {n, 1, Length[b]}]; If[x == d, a = Union[a]; l = Length[a]; d = 10 d; Print[l]; AppendTo[c, l]], {x, 1, 10000}]; c (*Artur Jasinski*)
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de), Sep 22 2008
EXTENSIONS
Fixed broken link, corrected and extended to agree with website. - Ray Chandler, Jun 30 2015
STATUS
approved