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%I #6 Jan 17 2019 16:53:42
%S 6,8,9,23,29,30,32,39,42,45,53,57,65,80,92,95,101,102,108,113,116,128,
%T 141,144,153,161,182,183,186,200,206,216,218,219,225,239,245,249,260,
%U 266,270,273,279,281,282,296,311,314,318,321
%N Natural numbers n such that the concatenation n//1331 is a prime number.
%C n is no multiple of 11 as 1331 = 11^3.
%C Necessarily n = 3 * k or n = 3 * k + 2, but not n = 3 * k + 1, because sod(1331) = 8.
%C Sequence is infinite, Dirichlet's prime number theorem for naturals of the form n * 10^4 + 1331.
%C For prefixed 1331 and references see A173836.
%e 61331 = prime(6169) => a(1) = 6.
%e 81331 = prime(7958) => a(2) = 8.
%t Select[Range[400],PrimeQ[#*10^4+1331]&] (* _Harvey P. Dale_, Jan 17 2019 *)
%o (PARI) isok(n) = isprime(n*10^4 + 1331); \\ _Michel Marcus_, Aug 27 2013
%Y A168327, A168417, A173836
%K base,nonn
%O 1,1
%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 12 2010
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