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A110604 Numbers n whose base 6 representations, interpreted as base 10 integers, are semiprimes.

%I A110604 #11 Oct 12 2019 12:00:50
%S A110604 4,6,10,11,13,14,17,21,22,23,31,35,43,47,49,50,51,57,58,61,62,63,65,
%T A110604 71,73,74,75,77,81,82,83,85,95,105,106,109,110,111,113,118,121,123,
%U A110604 130,131,133,143,147,151,153,155,158,173,175,177,178,181,182,185,187,190,191
%N A110604 Numbers n whose base 6 representations, interpreted as base 10 integers, are semiprimes.
%C A110604 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 A110604 a(1) = 4 because 4 (base 6) = 4 and 4 (base 10) = 2 * 2, a semiprime (A001358).
%e A110604 a(2) = 6 because 6 (base 6) = 10 and 10 (base 10) = 2 * 5.
%e A110604 a(3) = 10 because 10 (base 6) = 14 and 14 (base 10) = 2 * 7.
%e A110604 a(4) = 11 because 11 (base 6) = 15 and 15 (base 10) = 3 * 5.
%e A110604 a(5) = 13 because 13 (base 6) = 21 and 21 (base 10) = 3 * 7.
%t A110604 Select[Range[191], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 6]]] == 2 &] (* _Ray Chandler_, Aug 05 2005 *)
%t A110604 Select[Range[200],PrimeOmega[FromDigits[IntegerDigits[#,6]]]==2&] (* _Harvey P. Dale_, Oct 02 2011 *)
%Y A110604 Cf. A001358, A007092, A108873, A110602, A110603, A110605, A110606, A110607.
%K A110604 base,easy,nonn
%O A110604 1,1
%A A110604 _Jonathan Vos Post_, Jul 30 2005
%E A110604 Corrected and extended by _Ray Chandler_, Aug 05 2005