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 A236670 Start with 6; thereafter, primes obtained by concatenating to the end of previous term the next smallest number that will produce a prime. 0

%I #14 Nov 28 2014 22:55:29

%S 6,61,613,6131,613141,61314119,6131411917,61314119171,6131411917181,

%T 613141191718127,61314119171812789,613141191718127893,

%U 61314119171812789379,6131411917181278937929,61314119171812789379291,61314119171812789379291111

%N Start with 6; thereafter, primes obtained by concatenating to the end of previous term the next smallest number that will produce a prime.

%C a(n+1) is the next smallest prime beginning with a(n). Initial term is 6. After a(1), these are the primes arising in A069608.

%e a(1) = 6 by definition.

%e a(2) is the next smallest prime beginning with 6, so a(2) = 61.

%e a(3) is the next smallest prime beginning with 61, so a(3) = 613.

%o (Python)

%o import sympy

%o from sympy import isprime

%o def b(x):

%o ..num = str(x)

%o ..n = 1

%o ..while n < 10**3:

%o ....new_num = str(x) + str(n)

%o ....if isprime(int(new_num)):

%o ......print(int(new_num))

%o ......x = new_num

%o ......n = 1

%o ....else:

%o ......n += 1

%o b(6)

%Y Cf. A069608, A048553, A110773.

%K nonn,base

%O 1,1

%A _Derek Orr_, Jan 29 2014

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