Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #31 May 18 2022 07:56:56
%S 4,6,8,9,12,16,18,24,27,32,36,46,48,54,64,69,72,81,92,96,108,128,138,
%T 144,162,184,192,207,216,243,256,276,288,324,368,384,414,432,446,466,
%U 486,512,529,552,576,621,648,669,699,729,736,768,828,864,892,932,972
%N Composite numbers whose prime factors contain no digits other than 2 and 3.
%C All terms are a product of at least two terms of A020458. - _David A. Corneth_, Oct 09 2020
%H David A. Corneth, <a href="/A036310/b036310.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Vincenzo Librandi)
%H <a href="/index/Pri#prime_factors">Index entries for sequences related to prime factors</a>.
%F Sum_{n>=1} 1/a(n) = Product_{p in A020458} (p/(p - 1)) - Sum_{p in A020458} 1/p - 1 = 1.2804224166... . - _Amiram Eldar_, May 18 2022
%t dpfQ[n_]:=Module[{d=Union[Flatten[IntegerDigits/@Transpose[ FactorInteger[ n]][[1]]]]},!PrimeQ[n] && (d=={2}||d=={3}||d=={2,3})]; Select[Range[ 1000], dpfQ] (* _Harvey P. Dale_, Aug 24 2013 *)
%Y Cf. A003586, A020458, A036302-A036325.
%K nonn,easy,base
%O 1,1
%A _Patrick De Geest_, Dec 15 1998