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 A090684 Primes of the form 8n^2 - 1. 11
 7, 31, 71, 127, 199, 647, 967, 1151, 1567, 2311, 2591, 2887, 3527, 4231, 4999, 5407, 6271, 7687, 8191, 11551, 12799, 16927, 19207, 20807, 23327, 25087, 27847, 31751, 34847, 35911, 39199, 47431, 49927, 51199, 53791, 59167, 63367, 69191, 70687 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS In the odd number variant of the Ulam spiral, unimpeded by even numbers, prime numbers can line up in horizontal and vertical lines. But there are still noticeable diagonal lines of primes, and these primes fall on one such diagonal. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 MATHEMATICA Select[Table[8n^2 - 1, {n, 9000}], PrimeQ] (* Alonso del Arte, Mar 27 2011 *) PROG (PARI) mx2pmp(n, m) = { for(x=1, n, y = 8*x^2-1; if(isprime(y), print1(y", ")) ) } (MAGMA) [8*n^2-1: n in [1..95] | IsPrime(8*n^2-1)];  // Bruno Berselli, Mar 28 2011 CROSSREFS Sequence in context: A105428 A050547 A157914 * A033199 A304163 A003550 Adjacent sequences:  A090681 A090682 A090683 * A090685 A090686 A090687 KEYWORD easy,nonn AUTHOR Cino Hilliard, Dec 18 2003 STATUS approved

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Last modified October 21 16:50 EDT 2019. Contains 328302 sequences. (Running on oeis4.)