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%I #17 Jan 28 2023 08:02:36
%S 31,3001,30000001,30000000001,30000000000000000000000000001,
%T 3000000000000000000000000000000000001,
%U 30000000000000000000000000000000000000000000000000000000000000000001
%N Primes of the form 3*10^k + 1.
%H S. W. Golomb, <a href="http://www.jstor.org/stable/2005337">Properties of the sequence 3.2^n+1</a>, Math. Comp., 30 (1976), 657-663.
%H S. W. Golomb, <a href="/A004119/a004119.pdf">Properties of the sequence 3.2^n+1</a>, Math. Comp., 30 (1976), 657-663. [Annotated scanned copy]
%F a(n) = 3*10^A056807(n)+1. - _R. J. Mathar_, Jul 15 2015
%t Select[3*10^Range[70]+1,PrimeQ] (* _Harvey P. Dale_, Jul 05 2020 *)
%Y Cf. A199683, A056807, A062339.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Jul 08 2015
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