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 A306751 Numbers k such that 9*10^(2*k) + 3*10^k + 1 are prime. 1
 0, 5, 14, 77, 104, 2603, 2657 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..7. EXAMPLE 13 is prime ==> a(1) = 0. 931 = 7^2 * 19. 90301 = 73 * 1237. 9003001 = 7 * 757 * 1699. 900030001 = 13 * 4969 * 13933. 90000300001 is prime ==> a(2) = 5. PROG (PARI) for(k=0, 1e3, if(ispseudoprime(9*100^k+3*10^k+1), print1(k", "))) CROSSREFS Cf. A309738, A309743. Sequence in context: A197876 A305017 A007838 * A305341 A316611 A174939 Adjacent sequences: A306748 A306749 A306750 * A306752 A306753 A306754 KEYWORD nonn,base,more AUTHOR Seiichi Manyama, Aug 15 2019 STATUS approved

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Last modified June 6 04:47 EDT 2023. Contains 363139 sequences. (Running on oeis4.)