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A119729 a(1)=4, then a(n) is the smallest semiprime not occurring earlier, not ending with zero and starting with the last digit of a(n-1). 1

%I

%S 4,46,6,62,21,14,49,9,91,15,51,106,65,55,57,74,403,33,34,407,77,703,

%T 35,58,82,22,25,501,111,115,502,26,69,93,38,85,505,511,118,86,611,119,

%U 94,411,121,122,201,123,39,95,514,413,301,129,901,133,302,202,203,303,305

%N a(1)=4, then a(n) is the smallest semiprime not occurring earlier, not ending with zero and starting with the last digit of a(n-1).

%H David A. Corneth, <a href="/A119729/b119729.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Zak Seidov)

%Y Cf. A000030, A001358, A010879.

%K nonn,base,easy

%O 1,1

%A _Jonathan Vos Post_, Jun 14 2006

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Last modified April 22 22:19 EDT 2021. Contains 343197 sequences. (Running on oeis4.)