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A224217 Numbers b such that b^2 + 4*b + 9 is prime. 1
4, 10, 34, 46, 70, 76, 94, 112, 124, 160, 166, 196, 202, 244, 256, 292, 334, 340, 370, 412, 430, 454, 460, 490, 502, 514, 532, 550, 574, 586, 592, 622, 664, 712, 724, 754, 766, 784, 790, 796, 802, 832, 850, 874, 886, 916, 952, 994 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Inspired by Sun's conjecture in A224197: Also, bases b such that the number (with digits) [1;4;9] in base b is prime.
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,...)
LINKS
MATHEMATICA
Select[Range[1000], PrimeQ[#^2+4#+9]&] (* Harvey P. Dale, Sep 23 2020 *)
CROSSREFS
Sequence in context: A338296 A105680 A261577 * A066454 A301595 A022445
KEYWORD
nonn
AUTHOR
M. F. Hasler, Apr 01 2013
STATUS
approved

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Last modified March 29 08:59 EDT 2024. Contains 371268 sequences. (Running on oeis4.)