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 A303090 Numbers k such that 5^k + 2*k is prime. 1
 1, 2, 3, 7, 18, 27, 61, 721, 873, 2492, 8713 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(12) > 20000. - Jon E. Schoenfield, Apr 19 2018 a(12) > 40000. - Michael S. Branicky, Apr 13 2023 LINKS Table of n, a(n) for n=1..11. EXAMPLE 1 is a term because 5^1 + 2*1 = 5 + 2 = 7, a prime. 2 is a term because 5^2 + 2*2 = 25 + 4 = 29, a prime. 3 is a term because 5^3 + 2*3 = 125 + 6 = 131, a prime. MAPLE a:=k->`if`(isprime(5^k+2*k), k, NULL): seq(a(k), k=1..5500); PROG (GAP) Filtered([1..700], k->IsPrime(5^k+2*k)); (PARI) isok(k) = isprime(5^k + 2*k); \\ Altug Alkan, Apr 19 2018 CROSSREFS Cf. A299642, A299643, A297663. Sequence in context: A295509 A225747 A058334 * A131093 A359089 A343358 Adjacent sequences: A303087 A303088 A303089 * A303091 A303092 A303093 KEYWORD nonn,more AUTHOR Muniru A Asiru, Apr 18 2018 EXTENSIONS a(11) from Jon E. Schoenfield, Apr 18 2018 STATUS approved

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Last modified September 19 17:13 EDT 2024. Contains 376014 sequences. (Running on oeis4.)