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a(1) = 1, then the rearrangement of composite numbers such that the concatenation of n terms from the n-th term is a prime. (Concatenation of n-th term to (2n-1)th term is a prime number).
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%I #4 Dec 05 2013 19:56:14

%S 1,4,21,6,49,8,77,9,39,10,81,12,221,14,63,15,203,16,143,18,511,20,217,

%T 22,279,24,299,25,319,26,33,27,147,28,943,30,121,32,87,34,333,35,781,

%U 36,249,38,679,40,99,42,117,44,1463,45,697,46,187,48,207,50,219,51,639,52

%N a(1) = 1, then the rearrangement of composite numbers such that the concatenation of n terms from the n-th term is a prime. (Concatenation of n-th term to (2n-1)th term is a prime number).

%e 421, 21649, etc. are primes.

%Y Cf. A083193.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Apr 27 2003

%E Corrected a(11)=81 and extended by _Ray Chandler_, Jan 04 2009