A144850 a(n) = number of distinct prime divisors (taken together) of numbers of the form x^2+x+1 for x<=10^n.

8, 74, 734, 7233, 71653, 712026, 7090655, 70686855, 705173825, 7038475146, 70278276834, 701910715473

Offset

1,1

Links

Table of n, a(n) for n=1..12.

Bernhard Helmes, Prime sieving on the polynomial f(n)=n^2+n+1.

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*)

Crossrefs

Cf. A002383, A143835, A143868, A144848, A144851.

Sequence in context: A282880 A190953 A220458 * A337370 A357208 A163970

Adjacent sequences: A144847 A144848 A144849 * A144851 A144852 A144853

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