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 1-3 of 3 results.

A154112 Numbers k such that (k+1)^3 - k^2 is prime.

Original entry on oeis.org

1, 2, 4, 5, 6, 7, 9, 10, 11, 12, 16, 19, 20, 32, 34, 37, 42, 44, 45, 49, 51, 52, 56, 60, 62, 70, 72, 74, 75, 77, 79, 81, 89, 90, 95, 96, 97, 100, 101, 104, 105, 111, 114, 115, 121, 126, 131, 136, 145, 151, 154, 156, 161, 171, 174, 175, 180, 182, 191, 199, 200, 202, 207
Offset: 1

Views

Author

Keywords

Examples

			2^3-1^2 = 7, 3^3-2^2 = 23, ...
		

Crossrefs

Programs

  • Magma
    [n: n in [0..5000] | IsPrime(((n+1)^3-n^2))]; // Vincenzo Librandi, Nov 26 2010
    
  • Mathematica
    a[n_]:=(n+1)^3-n^2;lst={};Do[If[PrimeQ[a[n]],AppendTo[lst,n]],{n,6!}];lst
    Select[Range[210],PrimeQ[(#+1)^3-#^2]&] (* Harvey P. Dale, Sep 20 2011 *)
  • PARI
    is(n)=isprime((n+1)^3 - n^2) \\ Charles R Greathouse IV, Sep 02 2016

A154113 Primes of the form (n+1)^3 - n^2.

Original entry on oeis.org

7, 23, 109, 191, 307, 463, 919, 1231, 1607, 2053, 4657, 7639, 8861, 34913, 41719, 53503, 77743, 89189, 95311, 122599, 138007, 146173, 182057, 223381, 246203, 353011, 383833, 416399, 433351, 468623, 505759, 544807, 721079, 745471, 875711
Offset: 1

Views

Author

Keywords

Examples

			2^3-1^2=7, 3^3-2^2=23, ...
		

Crossrefs

Programs

  • Magma
    [a: n in [0..100] | IsPrime(a) where a is (n+1)^3 - n^2]; // Vincenzo Librandi, Sep 02 2016
    
  • Mathematica
    a[n_]:=(n+1)^3-n^2;lst={};Do[If[PrimeQ[a[n]],AppendTo[lst,a[n]]],{n,6!}];lst
    Select[(#+1)^3-#^2&/@Range[200],PrimeQ]  (* Harvey P. Dale, Mar 14 2011 *)
  • PARI
    for(n=1,1e3, if(isprime(t=(n+1)^3 - n^2), print1(t", "))) \\ Charles R Greathouse IV, Sep 02 2016

A154115 Numbers n such that n + 3 is prime.

Original entry on oeis.org

0, 2, 4, 8, 10, 14, 16, 20, 26, 28, 34, 38, 40, 44, 50, 56, 58, 64, 68, 70, 76, 80, 86, 94, 98, 100, 104, 106, 110, 124, 128, 134, 136, 146, 148, 154, 160, 164, 170, 176, 178, 188, 190, 194, 196, 208, 220, 224, 226, 230, 236, 238, 248, 254, 260, 266, 268, 274, 278
Offset: 1

Views

Author

Keywords

Examples

			a(2) = 2 since (2 + 2)^2 - (2 + 1)^2 - 2 = 5.
		

Crossrefs

Cf. A067076 (a(n-1)/2).

Programs

  • Magma
    [n: n in [0..500] | IsPrime((n+2)^2-(n+1)^2-n)]; // Vincenzo Librandi, Nov 26 2010
    
  • Maple
    A154115 := proc(n) ithprime(n+1)-3 ; end proc: # R. J. Mathar, May 09 2010
  • Mathematica
    a[n_]:=(n+2)^2-(n+1)^2-n;lst={};Do[If[PrimeQ[a[n]],AppendTo[lst,n]],{n,6!}];lst
    Select[Range[0,300],PrimeQ[(#+2)^2-(#+1)^2-#]&] (* Harvey P. Dale, Nov 06 2013 *)
    Prime[Range[2,100]]-3 (* Harvey P. Dale, Jul 15 2017 *)
  • PARI
    is(n)=isprime(n+3) \\ Charles R Greathouse IV, Sep 02 2016

Formula

a(n) = A086801(n+1). - R. J. Mathar, May 09 2010

Extensions

New name based on a comment by Franklin T. Adams-Watters, Jan 30 2009
Showing 1-3 of 3 results.