This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A140330 #10 Jul 21 2017 16:21:52
%S A140330 1,6,14,15,55,63,247,255,511,1023,2047,4095,12287,16383,32767,65535,
%T A140330 196607,262143,983039,1048575,2097151,4194303,8388607,16777215,
%U A140330 33554431,67108863,134217727,268435455,536870911,1073741823,3221225471
%N A140330 Smallest nonprime with Hamming weight n (i.e., with exactly n 1's when written in binary).
%C A140330 Apart from the first term, identical to A089226. - _R. J. Mathar_, May 31 2008
%F A140330 a(n) = MIN{k such that k is in A018252 and A000120(k) = n}.
%e A140330 a(10) = 1023 because 1023 base 2 = 1111111111 which has 10 1's and 1023 = 3 * 11 * 31 is nonprime.
%Y A140330 Cf. A061712.
%K A140330 easy,base,nonn
%O A140330 1,2
%A A140330 _Jonathan Vos Post_, May 26 2008
%E A140330 More terms from _R. J. Mathar_, May 31 2008