OFFSET
1,2
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).
LINKS
Bruno Berselli, Table of n, a(n) for n = 1..1000
Umberto Cerruti, I numeri idonei di Eulero (in Italian), p. 3.
Leonhard Euler, An easy method for finding many very large prime numbers, p. 8, arXiv:math/0507401 [math.HO], 2005-2008. Translated from Latin.
MATHEMATICA
Select[Range[200], PrimeQ[232 #^2 + 1] &]
PROG
(Magma) [n: n in [1..200] | IsPrime(232*n^2+1)];
(PARI) is(n)=isprime(232*n^2+1) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Bruno Berselli, Oct 18 2013
STATUS
approved