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%I #11 Oct 12 2019 12:00:50
%S 4,6,10,11,13,14,17,21,22,23,31,35,43,47,49,50,51,57,58,61,62,63,65,
%T 71,73,74,75,77,81,82,83,85,95,105,106,109,110,111,113,118,121,123,
%U 130,131,133,143,147,151,153,155,158,173,175,177,178,181,182,185,187,190,191
%N Numbers n whose base 6 representations, interpreted as base 10 integers, are semiprimes.
%C A108873 is the equivalent using base 3. A110602 is the equivalent using base 4. A110603 is the equivalent using base 5. A110605 is the equivalent using base 7. A110606 is the equivalent using base 8. A110607 is the equivalent using base 9.
%e a(1) = 4 because 4 (base 6) = 4 and 4 (base 10) = 2 * 2, a semiprime (A001358).
%e a(2) = 6 because 6 (base 6) = 10 and 10 (base 10) = 2 * 5.
%e a(3) = 10 because 10 (base 6) = 14 and 14 (base 10) = 2 * 7.
%e a(4) = 11 because 11 (base 6) = 15 and 15 (base 10) = 3 * 5.
%e a(5) = 13 because 13 (base 6) = 21 and 21 (base 10) = 3 * 7.
%t Select[Range[191], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 6]]] == 2 &] (* _Ray Chandler_, Aug 05 2005 *)
%t Select[Range[200],PrimeOmega[FromDigits[IntegerDigits[#,6]]]==2&] (* _Harvey P. Dale_, Oct 02 2011 *)
%Y Cf. A001358, A007092, A108873, A110602, A110603, A110605, A110606, A110607.
%K base,easy,nonn
%O 1,1
%A _Jonathan Vos Post_, Jul 30 2005
%E Corrected and extended by _Ray Chandler_, Aug 05 2005
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