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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A230391 Numbers m such that 232*m^2+1 is prime.

Original entry on oeis.org

1, 2, 3, 5, 6, 7, 9, 10, 12, 13, 15, 16, 17, 18, 20, 22, 24, 26, 27, 28, 31, 35, 36, 37, 38, 44, 45, 46, 48, 49, 50, 52, 53, 62, 67, 71, 72, 73, 74, 76, 79, 81, 82, 86, 87, 94, 95, 99, 100, 104, 106, 107, 112, 113, 115, 118, 119, 121, 124, 126, 127, 136, 138
Offset: 1

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Author

Bruno Berselli, Oct 18 2013

Keywords

Comments

The form "232aa + 1" has been used by Euler to find idoneal numbers (A000926), and 232 itself is an idoneal number (see References).
Numbers m for which 232*m^2+1 is not prime are: 0, 4, 8, 11, 14, 19, 21, 23, 25, 29, 30, 32, 33, 34, 39, 40, 41, 42, 43, 47, ... (see table on page 14 of Euler's paper).

References

  • Leonhard Euler, Facillima methodus plurimos numeros primos praemagnos inveniendi, Nova Acta Academiae Scientiarum Imperialis Petropolitanae Tomus XIV (1805), Mathematica et Physico-Mathematica (this sequence is on page 10).

Crossrefs

Cf. A000926, A230392 (associated primes).

Programs

  • Magma
    [n: n in [1..200] | IsPrime(232*n^2+1)];
    
  • Mathematica
    Select[Range[200], PrimeQ[232 #^2 + 1] &]
  • PARI
    is(n)=isprime(232*n^2+1) \\ Charles R Greathouse IV, Jun 06 2017
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