cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-4 of 4 results.

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

Views

Author

Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de), Sep 22 2008, Sep 24 2008

Keywords

Links

Crossrefs

For primes of the form n^2+1 see A002496.
Cf. A002496, A143835, A143868, A144850, A144851.

Programs

  • Mathematica
    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 *)

Extensions

Fixed broken link 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

Views

Author

Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de), Sep 22 2008

Keywords

Links

Crossrefs

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

Programs

  • 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*)

Extensions

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

Views

Author

Artur Jasinski & Bernhard Helmes (bhelmes(AT)gmx.de), Sep 22 2008

Keywords

Comments

Primes of the form 4x^2+1 see A121326(n) = A002496(n+1).

Links

Crossrefs

Cf. A002383, A121326, A143835, A143868, A144848, A144850, A144851.

Programs

  • Mathematica
    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*)

Extensions

Fixed broken link, corrected and extended to agree with website. - Ray Chandler, Jun 30 2015

A145688 Primitive prime factors of the sequence 2k^2 + 1 in the order that they are found.

Original entry on oeis.org

3, 19, 11, 17, 73, 43, 163, 67, 113, 131, 41, 193, 59, 241, 89, 883, 353, 1153, 139, 1459, 523, 1801, 641, 683, 2179, 257, 2593, 83, 107, 179, 97, 3529, 137, 1291, 4051, 491, 419, 1601, 1667, 601, 1873, 307, 2017, 2243, 211, 379, 827, 233, 467, 2731, 313, 8713
Offset: 1

Views

Author

Bernhard Helmes (pi(AT)devalco.de), Oct 16 2008

Keywords

Comments

a(n) mod 8 = 1 or 3.

Links

Crossrefs

Cf. A144851.
Showing 1-4 of 4 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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