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 A247241 #19 Mar 29 2015 17:33:47 %S A247241 2,19,558,272060,34949682936,297564712194085870576, %T A247241 10932581082490851526951746612437309648864, %U A247241 7425338450010038712278392695279246718801455644988538421150211866664645481447360 %N A247241 In base 2, smallest positive integer k such that k contains all possible strings of n binary digits. %C A247241 In base 2, there are 2^n distinct strings of n digits and the smallest positive integer to contain all of them will have 2^n+(n-1) digits (see A052944). For example, there are 2^2 = 4 distinct strings of two digits: 00, 01, 10, 11. All of them are represented in the 5-digit binary number 10011 = 19 in base 10. %H A247241 Anthony Sand, <a href="/A247241/b247241.txt">Table of n, a(n) for n = 1..12</a> %e A247241 n = 1: a(1) = 2 = 10 in base 2, which contains 2 distinct strings of one digit: 1, 0. %e A247241 n = 2: a(2) = 19 = 10011, which contains 4 distinct strings of two digits: 10, 00, 01, 11. %e A247241 n = 3: a(3) = 558 = 1000101110, which contains 8 distinct strings of three digits: 100, 000, 001, 010, 101, 011, 111, 110. %e A247241 n = 4: a(4) = 272060 = 1000010011010111100, which contains 16 distinct strings of four digits: 1000, 0000, 0001, 0010, 0100, 1001, 0011, 0110, 1101, 1010, 0101, 1011, 0111, 1111, 1110, 1100. %Y A247241 Cf. A249907, A033008. %K A247241 nonn,base %O A247241 1,1 %A A247241 _Anthony Sand_, Nov 28 2014