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 A301634 Numbers k such that 2^k + 2*k + 1 is prime. 3
 0, 1, 5, 13, 65, 85, 229, 2005, 3875, 3919, 5417, 8819, 11899, 16668, 19445, 28242, 37918, 40594 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Next term, if it exists, is greater than 50000. Terms up to 229 correspond to provable primes. The terms greater than or equal to 2005 correspond to probable primes. - Jon E. Schoenfield and Vaclav Kotesovec, Mar 27 2018 LINKS MAPLE a:=k->`if`(isprime(2^k+2*k+1), k, NULL): seq(a(k), k=0..6000); # Muniru A Asiru, Mar 25 2018 MATHEMATICA Flatten[{0, Select[Range[5000], PrimeQ[2^# + 2*# + 1] &]}] (* Vaclav Kotesovec, Mar 25 2018 *) PROG (PARI) for(n=0, 500, if(isprime(2^n+2*n+1), print1(n", "))) CROSSREFS A163115 gives the primes. Numbers k such that b^k + b*k + 1 is prime: this sequence (b=2), A171058 (b=3), A301635 (b=5). Cf. A176691. Sequence in context: A149572 A149573 A149574 * A309167 A272069 A018678 Adjacent sequences:  A301631 A301632 A301633 * A301635 A301636 A301637 KEYWORD nonn,more,hard AUTHOR Seiichi Manyama, Mar 25 2018 EXTENSIONS a(9)-a(15) from Vaclav Kotesovec, Mar 25 2018 a(16)-a(18) from Jon E. Schoenfield, Mar 26 2018 STATUS approved

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Last modified September 30 18:12 EDT 2020. Contains 337440 sequences. (Running on oeis4.)