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 A115454 #18 Aug 17 2018 09:24:09 %S A115454 100,110,1000,1001,1010,1100,1110,1111,10000,10010,10100,10101,10110, %T A115454 11000,11001,11010,11011,11100,11110,100000,100001,100010,100011, %U A115454 100100,100110,100111,101000,101010,101100,101101,101110,110000,110001 %N A115454 Composite positive integers written in base 2. %C A115454 If n is in the sequence then so is 10 * n. - _David A. Corneth_, Aug 17 2018 %H A115454 Robert Israel, <a href="/A115454/b115454.txt">Table of n, a(n) for n = 1..10000</a> %F A115454 a(n) = A007088(A002808(n)). %p A115454 map(convert,remove(isprime, [$4..200]),binary); # _Robert Israel_, Aug 17 2018 %t A115454 For[n = 2, n < 50, n++, If[Not[PrimeQ[n]], Print[BaseForm[n, 2]]]] (* _Stefan Steinerberger_, Jan 24 2006 *) %o A115454 (PARI) lista(nn) = forcomposite(n=1, nn, print1(fromdigits(binary(n), 10), ", ")); \\ _Michel Marcus_, Aug 17 2018 %Y A115454 Cf. A002808, A007088, A004676. %K A115454 base,nonn %O A115454 1,1 %A A115454 _Leroy Quet_, Jan 22 2006 %E A115454 More terms from _Stefan Steinerberger_, Jan 24 2006