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.

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A107295 Numbers k such that prime(k^2) - k^2 is prime.

Original entry on oeis.org

2, 4, 12, 14, 20, 42, 48, 56, 60, 88, 104, 120, 126, 134, 138, 160, 164, 182, 186, 204, 226, 254, 270, 276, 312, 316, 330, 336, 350, 382, 408, 410, 414, 422, 438, 448, 450, 480, 492, 494, 502, 522, 546, 568, 580, 596, 620, 624, 640, 650, 690, 696
Offset: 1

Views

Author

Zak Seidov, May 20 2005

Keywords

Examples

			88 is in the sequence because prime(88^2) - 88^2 = prime(7744) - 7744 = 78977 - 7744 = 71233 = prime(7051).

Crossrefs

Cf. A064269 (prime(n)-n is prime), A141129 (prime(n^2)-n^2).

Programs

  • Mathematica
    Select[Range[700],PrimeQ[Prime[#^2]-#^2]&] (* Harvey P. Dale, Jun 20 2015 *)
  • PARI
    isok(n) = isprime(prime(n^2) - n^2); \\ Michel Marcus, Oct 09 2013

Extensions

More terms from Michel Marcus, Oct 09 2013

A141127 a(n) = prime(prime(n*n) - n*n) - n*n where prime(n) is the n-th prime.

Original entry on oeis.org

1, 1, 34, 141, 334, 595, 1012, 1503, 2192, 2983, 3786, 4963, 6304, 7687, 9518, 11017, 13122, 15277, 17760, 20373, 23312, 26695, 29742, 33365, 37338, 41175, 45580, 50217, 54762, 59549, 65332, 71067, 76712, 82765, 88692, 95657, 102814, 110385
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Jul 31 2008

Keywords

Examples

			a(1) = prime(prime(1*1) - 1*1) - 1*1 = prime(prime(1) - 1) - 1 = prime(2 - 1) - 1 = prime(1) - 1 = 2 - 1 = 1.
a(5) = prime(prime(5*5) - 5*5) - 5*5 = prime(prime(25) - 25) - 25 = prime(97 - 25) - 25 = prime(72) - 25 = 359 - 25 = 334.

Crossrefs

Cf. A014689, A141129.

Programs

  • Maple
    p:=ithprime: seq(p(p(n^2)-n^2)-n^2,n=1..40); # Emeric Deutsch, Aug 16 2008
  • Mathematica
    a[n_]:=Prime[Prime[n*n]-n*n]-n*n;Array[a,38] (* James C. McMahon, Jul 17 2025 *)

Extensions

Corrected and extended by Emeric Deutsch, Aug 16 2008
Showing 1-2 of 2 results.

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