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%I #8 Nov 18 2018 00:45:02
%S 3,6,18,54,162,486,972,1944,5832,40824,204120,408240,816480,1632960,
%T 3265920,6531840,26127360,130636800,391910400,1175731200,14108774400,
%U 56435097600,1241572147200,8691005030400,26073015091200,260730150912000
%N a(1) = 3, a(n) = smallest multiple of a(n-1) such that 10*a(n) + 1 is prime.
%e 31, 61, 181, etc. are primes.
%t k = 3; Print[k]; Do[i = 2; While[ !PrimeQ[10*i*k + 1], i++ ]; k *= i; Print[k], {n, 1, 30}] (* _Ryan Propper_, Aug 06 2005 *)
%Y Cf. A089326.
%K base,nonn,easy
%O 1,1
%A _Amarnath Murthy_, Nov 03 2003
%E More terms from _Ryan Propper_, Aug 06 2005
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