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.

A052074 Squares of primes p^2 with the property that nextprime(p) is a substring of p^2.

Original entry on oeis.org

529, 6889, 12769, 1261129, 40001200009, 107667328129, 145381301521, 510649971459777361, 24172491655282243145798689
Offset: 1

Views

Author

Patrick De Geest, Jan 15 2000

Keywords

Examples

			The corresponding primes p are 23, 83, 113, 1123, 200003, 328127, ..., the "next primes" are 29, 89, 127, 1129, 200009, 328129, ..., and these numbers are indeed substrings of 529, 6889, 12769, 1261129, 40001200009, 107667328129, ...
		

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range[37*10^6]]^2,SequenceCount[IntegerDigits[#], IntegerDigits[ NextPrime[ Sqrt[#]]]]>0&] (* The program uses the SequenceCount function from Mathematica version 10 *) (* Harvey P. Dale, Jul 13 2016 *)

Extensions

a(8) from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Sep 04 2006
Definition clarified and offset changed by N. J. A. Sloane, Jul 13 2016
a(9) from Giovanni Resta, May 24 2018

A052076 List of cubes p^3 of primes with property that next prime after p is a substring of p^3.

Original entry on oeis.org

1331, 1030301, 11224377919, 40343019516073, 83964379378069, 153551511228149, 153548930496746303, 214889691497505989703913, 79943078473759892945966959, 16573430415736921632549592733, 22837138677705447754568672309, 940309072235302647342697969346063
Offset: 1

Views

Author

Patrick De Geest, Jan 15 2000

Keywords

Crossrefs

Programs

  • Mathematica
    f[0]=8;f[n_]:=Module[{i=PrimePi[f[n-1]^(1/3)]+1},
    While[StringPosition[ToString[Prime[i]^3],ToString[NextPrime[Prime[i]]]]=={}, i++];Prime[i]^3];f/@Range[7] (* Ivan N. Ianakiev, Nov 16 2016 *)
    #^3&/@Select[Prime[Range[10^6]],SequenceCount[IntegerDigits[#^3],IntegerDigits[ NextPrime[ #]]]> 0&] (* Harvey P. Dale, Jul 29 2023 *)

Extensions

More terms from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Sep 12 2006
Definition clarified by Charles R Greathouse IV, Dec 24 2014
a(12) from Giovanni Resta, Jul 02 2018

A383607 Square array read by antidiagonals upwards: T(n,k) is the smallest k-digit prime p such that nextprime(p) is a substring of p^n; or -1 if no such prime exists, n>1, k>0.

Original entry on oeis.org

-1, -1, 23, -1, 11, 113, 2, 37, 101, 1123, 7, 17, 487, 2239, -1, 5, 47, -1, 5659, 34297, 200003, 3, 13, -1, 2399, 91801, 535487, -1, -1, 31, 607, 1279, 31627, 842483, -1, -1, 3, 41, 431, 3163, 12281, 825059, 6315629, 59897017, 714597769, -1, 37, 233, 1931, 15791, 179947, 5623421, -1, 430784719, -1
Offset: 2

Views

Author

Jean-Marc Rebert, May 01 2025

Keywords

Examples

			T(2,3) = 113, because nextprime(113) = 127 is a substring in 113^2 = 12769, starting at position 1, and no smaller 3-digit prime satisfies this condition.
Top left corner begins at T(2,1):
  -1, 23, 113, 1123, ...
  -1, 11, 101, 2239, ...
  -1, 37, 487, 5659, ...
   2, 17,  -1, 2399, ...
  .., .., ..., ...., ...
		

Crossrefs

Programs

  • PARI
    T(n,k) = forprime(p=10^(k-1), 10^k-1, if (#strsplit(Str(p^n), Str(nextprime(p+1))) >= 2, return(p));); return(-1); \\ Michel Marcus, May 02 2025
Showing 1-3 of 3 results.