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A144850
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a(n) = number of distinct prime divisors (taken together) of numbers of the form x^2+x+1 for x<=10^n
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4
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8, 74, 734, 7233, 71653, 712026, 7090655, 70686855, 705173824, 7038475146, 70278276833
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| B. Helmes, quadratisches Siebverfahren/Primzahlgenerator
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MATHEMATICA
| d = 10; l = 0; p = 1; c = {}; a = {}; Do[k = p x^2 + x + 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*)
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CROSSREFS
| A002383, A143835, A143868, A144848, A144849, A144850, A144851
Sequence in context: A137140 A187529 A190953 * A163970 A116251 A166084
Adjacent sequences: A144847 A144848 A144849 * A144851 A144852 A144853
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KEYWORD
| base,nonn
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AUTHOR
| Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de) (grafix(AT)csl.pl), Sep 22 2008
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