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.

A153041 Numbers n >=10 such that 2*n-19 is not a prime.

Original entry on oeis.org

10, 14, 17, 20, 22, 23, 26, 27, 29, 32, 34, 35, 37, 38, 41, 42, 44, 47, 48, 50, 52, 53, 55, 56, 57, 59, 62, 65, 67, 68, 69, 70, 71, 72, 74, 76, 77, 80, 81, 82, 83, 86, 87, 89, 90, 92, 94, 95, 97, 98, 101, 102, 103, 104
Offset: 1

Views

Author

Vincenzo Librandi, Dec 17 2008

Keywords

Comments

One more than associated values in A153051, two more than A153047. - R. J. Mathar, Jan 05 2011
The terms after a(1) are the values of 2*h*k + k + h + 10, where h and k are positive integers.- Vincenzo Librandi, Jan 19 2013

Crossrefs

Numbers n such that 2n-k is not prime: A104275 (k=1), A153043 (k=3), A153040 (k=5), A153039 (k=7), A153044 (k=9), A153045 (k=11), A153049 (k=13), A153047 (k=15), A153051 (k=17), A153041 (k=19).
Similar sequence listed also in A089559, A153144.

Programs

  • Magma
    [n: n in [10..150] | not IsPrime(2*n - 19)]; // Vincenzo Librandi, Jan 19 2013
  • Mathematica
    Select[Range[10, 200], !PrimeQ[2 # - 19] &] (* Vincenzo Librandi, Jan 19 2013 *)

Extensions

Edited by N. J. A. Sloane, Jun 22 2010

A153047 Numbers n such that 2*n-15 is not a prime.

Original entry on oeis.org

12, 15, 18, 20, 21, 24, 25, 27, 30, 32, 33, 35, 36, 39, 40, 42, 45, 46, 48, 50, 51, 53, 54, 55, 57, 60, 63, 65, 66, 67, 68, 69, 70, 72, 74, 75, 78, 79, 80, 81, 84, 85, 87, 88, 90, 92, 93, 95, 96, 99, 100, 101, 102, 105, 108, 109, 110, 111, 112, 114, 115, 116
Offset: 1

Views

Author

Vincenzo Librandi, Dec 17 2008

Keywords

Comments

One more than the associated entry in A153049. - R. J. Mathar, Jan 05 2011
The terms are the values of 2*h*k + k + h + 8, where h and k are positive integers.- Vincenzo Librandi, Jan 19 2013

Crossrefs

Programs

A163652 Triangle read by rows where T(n,m)=2*m*n + m + n + 6.

Original entry on oeis.org

10, 13, 18, 16, 23, 30, 19, 28, 37, 46, 22, 33, 44, 55, 66, 25, 38, 51, 64, 77, 90, 28, 43, 58, 73, 88, 103, 118, 31, 48, 65, 82, 99, 116, 133, 150, 34, 53, 72, 91, 110, 129, 148, 167, 186, 37, 58, 79, 100, 121, 142, 163, 184, 205, 226, 40, 63, 86, 109, 132, 155, 178
Offset: 1

Views

Author

Vincenzo Librandi, Aug 02 2009

Keywords

Comments

The numbers 2*T(n,m)-11 = (2*n+1)*(2*m+1) are not prime, and 2*T(n,n) = (2n+1)^2.
First column: A112414, second column: A016885, third column: A017005, fourth column: A017173. - Vincenzo Librandi, Nov 20 2012

Examples

			Triangle begins:
  10;
  13, 18;
  16, 23, 30;
  19, 28, 37, 46;
  22, 33, 44, 55,  66;
  25, 38, 51, 64,  77,  90;
  28, 43, 58, 73,  88,  103, 118;
  31, 48, 65, 82,  99,  116, 133, 150;
  34, 53, 72, 91,  110, 129, 148, 167, 186;
  37, 58, 79, 100, 121, 142, 163, 184, 205, 226;
  40, 63, 86, 109, 132, 155, 178, 201, 224, 247, 270;
  etc.
		

Crossrefs

Programs

  • Magma
    [2*n*k + n + k + 6: k in [1..n], n in [1..11]]; // Vincenzo Librandi, Nov 20 2012
  • Mathematica
    t[n_,k_]:=2 n*k + n + k +  6; Table[t[n, k], {n, 15}, {k, n}]//Flatten (* Vincenzo Librandi, Nov 20 2012 *)

Formula

T(n,m) = A154685(n,m)+2 = A163657(n,m)-2. [R. J. Mathar, Oct 22 2009]

Extensions

Comment clarified by R. J. Mathar, Oct 22 2009
Showing 1-3 of 3 results.