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 A138823 #11 Apr 01 2017 15:44:48 %S A138823 1,10,100,1000,11111,111110,1111100,11111000 %N A138823 Divisors of 248 (the 3rd perfect number divided by 2), written in base 2. %C A138823 248 is the number of dimensions of E_8. %C A138823 a(n) has n digits. %H A138823 <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a> %e A138823 The structure of divisors of 248 (see A018355) %e A138823 .................................................................. %e A138823 n ............ Divisor . Formula ....... Divisor written in base 2 %e A138823 .................................................................. %e A138823 1) ................. 1 = 2^0 ........... 1 %e A138823 2) ................. 2 = 2^1 ........... 10 %e A138823 3) ................. 4 = 2^2 ........... 100 %e A138823 4) A134708(3) = .... 8 = 2^3 ........... 1000 %e A138823 5) A000668(3) = ... 31 = 2^5 - 2^0 ..... 11111 %e A138823 6) ................ 62 = 2^6 - 2^1 ..... 111110 %e A138823 7) ............... 124 = 2^7 - 2^2 ..... 1111100 %e A138823 8) A133028(3) = .. 248 = 2^8 - 2^3 ..... 11111000 %t A138823 FromDigits[IntegerDigits[#,2]]&/@Divisors[248] (* _Harvey P. Dale_, Apr 01 2017 *) %o A138823 (PARI) divisors(248) \\ _Charles R Greathouse IV_, Sep 06 2016 %Y A138823 Perfect number divided by 2: A133028. Cf. A000043, A000396, A000668, A018355, A090748, A134708, A135653. %K A138823 easy,fini,full,nonn,less %O A138823 1,2 %A A138823 _Omar E. Pol_, Mar 31 2008, corrected Apr 03 2008