A143868
a(n)= Number of distinct prime divisors (taken together) of numbers of the form 2x^2-1 for x<=10^n.
Original entry on oeis.org
8, 84, 815, 7922, 77250, 759077, 7492588, 74198995, 736401956, 7319543972, 72834161468, 725344237597
Offset: 1
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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[N[Log[x]/Log[10]] == Round[N[Log[x]/Log[10]]], a = Union[a]; l = Length[a]; Print[l]; AppendTo[c, l]], {x, 1, 10000}]; c (*Artur Jasinski*)
Fixed broken link and corrected terms to agree with website -
Ray Chandler, Jun 30 2015
A144848
a(n) = number of distinct prime divisors (taken together) of numbers of the form x^2+1 for x<=10^n.
Original entry on oeis.org
7, 70, 720, 7102, 70780, 704537, 7026559, 70122424, 700184485, 6993568566, 69870544960, 698175242376
Offset: 1
Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de), Sep 22 2008, Sep 24 2008
For primes of the form n^2+1 see
A002496.
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d = 10; l = 0; p = 1; 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 *)
Fixed broken link and extended to agree with website. -
Ray Chandler, Jun 30 2015
A144851
a(n) = number of distinct prime divisors (taken together) of numbers of the form 2x^2+1 for x<=10^n.
Original entry on oeis.org
8, 76, 760, 7445, 73477, 726948, 7218256, 71801859, 715087632, 7127665635, 71089166879, 709344259821
Offset: 1
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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*)
Fixed broken link, corrected and extended to agree with website. -
Ray Chandler, Jun 30 2015
A144850
a(n) = number of distinct prime divisors (taken together) of numbers of the form x^2+x+1 for x<=10^n.
Original entry on oeis.org
8, 74, 734, 7233, 71653, 712026, 7090655, 70686855, 705173825, 7038475146, 70278276834, 701910715473
Offset: 1
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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*)
Fixed broken link, corrected and extended to agree with website. -
Ray Chandler, Jun 30 2015
A144852
a(n) = number of distinct prime divisors (taken together) of numbers of the form 4x^2+1 for x<=10^n.
Original entry on oeis.org
9, 87, 836, 8000, 78124, 766585, 7556731, 74771106, 741554656, 7366252759, 73261462211, 729280694469
Offset: 1
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d = 10; l = 0; p = 4; 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*)
Fixed broken link, corrected and extended to agree with website. -
Ray Chandler, Jun 30 2015
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