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 A078402 Numbers k such that k^2 + 5 is prime. 20
 0, 6, 12, 36, 48, 72, 78, 96, 114, 126, 162, 168, 198, 204, 246, 258, 294, 336, 342, 372, 414, 432, 456, 462, 492, 504, 516, 534, 552, 576, 588, 594, 624, 666, 714, 726, 756, 768, 786, 792, 798, 804, 834, 852, 876, 888, 918, 954, 996 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sum of the reciprocals of the primes generated from these indices converges to 0.2332142.. The sum of the reciprocals of these indices cannot be computed. All terms are divisible by 6. - Zak Seidov, Dec 27 2014 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Eric Weisstein's World of Mathematics, Near-Square Prime FORMULA a(n) = 6 * A056906(n). MATHEMATICA Select[Range[0, 1000], PrimeQ[#^2+5]&] (* Vincenzo Librandi, Jul 13 2012 *) PROG (PARI) for(n=0, 10^4, q=n^2+5; if(isprime(q), print1(n, ", "))); (MAGMA( [n: n in [0..1000]| IsPrime(n^2+5)]; // Vincenzo Librandi, Jul 15 2012 CROSSREFS For the primes see A056905(n). Other sequences of the type "Numbers k such that k^2 + i is prime": A005574 (i=1), A067201 (i=2), A049422 (i=3), A007591 (i=4), this sequence (i=5), A114269 (i=6), A114270 (i=7), A114271 (i=8), A114272 (i=9), A114273 (i=10), A114274 (i=11), A114275 (i=12). Sequence in context: A192029 A166636 A167338 * A127845 A096932 A212976 Adjacent sequences:  A078399 A078400 A078401 * A078403 A078404 A078405 KEYWORD nonn,easy AUTHOR Cino Hilliard, Dec 26 2002 EXTENSIONS Offset corrected by Arkadiusz Wesolowski, Aug 09 2011 STATUS approved

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Last modified August 16 23:58 EDT 2018. Contains 313809 sequences. (Running on oeis4.)