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 A224217 Numbers b such that b^2 + 4*b + 9 is prime. 1

%I

%S 4,10,34,46,70,76,94,112,124,160,166,196,202,244,256,292,334,340,370,

%T 412,430,454,460,490,502,514,532,550,574,586,592,622,664,712,724,754,

%U 766,784,790,796,802,832,850,874,886,916,952,994

%N Numbers b such that b^2 + 4*b + 9 is prime.

%C Inspired by Sun's conjecture in A224197: Also, bases b such that the number (with digits) [1;4;9] in base b is prime.

%C All terms are congruent to 4 (mod 6), i.e., a(n) = 4 + 6 x(n) with x=(0, 1, 5, 7, 11, 12, 15, 18, 20, 26, 27, 32, 33, 40, 42, 48, 55, 56, 61, 68, 71, 75, 76,...)

%t Select[Range[1000],PrimeQ[#^2+4#+9]&] (* _Harvey P. Dale_, Sep 23 2020 *)

%K nonn

%O 1,1

%A _M. F. Hasler_, Apr 01 2013

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Last modified January 27 17:42 EST 2023. Contains 359845 sequences. (Running on oeis4.)