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 A023251 Primes that remain prime through 2 iterations of function f(x) = 4x + 9. 4
 7, 41, 43, 47, 67, 71, 97, 103, 137, 263, 293, 307, 397, 421, 467, 491, 571, 587, 593, 683, 727, 757, 883, 907, 1021, 1061, 1063, 1097, 1153, 1373, 1427, 1433, 1453, 1523, 1567, 1657, 1747, 1811, 1867, 2141, 2251, 2281, 2287, 2647, 2693, 2791, 2797, 2857, 2927 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes p such that 4*p+9 and 16*p+45 are also primes. - Vincenzo Librandi, Aug 04 2010 LINKS John Cerkan, Table of n, a(n) for n = 1..10000 MATHEMATICA rpQ[n_]:=AllTrue[Rest[NestList[4#+9&, n, 2]], PrimeQ]; Select[Prime[ Range[ 500]], rpQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 03 2019 *) PROG (MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(4*n+9) and IsPrime(16*n+45)] // Vincenzo Librandi, Aug 04 2010 CROSSREFS Subsequence of A111199. Sequence in context: A165397 A123747 A144421 * A073501 A080666 A224718 Adjacent sequences:  A023248 A023249 A023250 * A023252 A023253 A023254 KEYWORD nonn AUTHOR STATUS approved

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Last modified May 26 21:56 EDT 2022. Contains 354092 sequences. (Running on oeis4.)