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%I #23 Feb 16 2020 20:56:16
%S 0,4,2,7,3,1,5,9,6,8,13,15,18,19,51,31,33,36,37,22,24,27,28,60,40,42,
%T 45,46,81,54,55,59,63,64,68,69,131,82,72,73,77,78,133,136,86,87,222,
%U 224,227,228,137,240,90,91,95,96,313,151,315,154,242,245,155,159,181,318,182,246,319,186,331,333,187,272,273,190,404,277,278,191,336,337,281,360,406,363,195,196,364,282,286,368,287,369,513,372,409,515,422,424,518
%N a(1) = 0; a(n) = smallest integer not yet in this sequence S such that two neighboring digits of S sum to a semiprime (4, 6, 9, 10, 14, or 15).
%C This is to A001358 (semiprimes) as Eric Angelini's "Smallest integer not yet in S such that two neighboring digits of S sum up to a prime", is to A000040 (primes). Corrected and extended by Hans Havermann.
%e a(2) = 4 because 4 is the smallest integer k such that a(0) + k is a semiprime (2*2 = 4).
%Y Cf. A001358.
%K nonn,base,easy
%O 1,2
%A _Jonathan Vos Post_, Apr 27 2012
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