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 A119408 #26 Dec 31 2021 17:55:48
%S A119408 1,9,273,33825,17043521,34630287489,282578800148737,
%T A119408 9241421688590303745,1210107565283851686118401,
%U A119408 634134936313486520338360567809,1329552593586084350528447794605199361,11151733894906779683522195341810241573494785
%N A119408 Decimal equivalent of the binary string generated by the n X n identity matrix.
%C A119408 a(n) is divisible by 2^n - 1. a(n) == n mod 2^(n+1) - 1. - _Robert Israel_, Jun 09 2015
%H A119408 Harvey P. Dale, <a href="/A119408/b119408.txt">Table of n, a(n) for n = 1..57</a>
%F A119408 a(n) = 2^((n+1)(n-1)) + 2^((n+1)(n-2)) + ... + 1 where n=2,3,...
%F A119408 a(n) = (2^n*2^(n^2)-1)/(2*2^n-1). - _Stuart Bruff_, Jun 08 2015
%e A119408 n=2: [1 0; 0 1] == 1001_2 = 9;
%e A119408 n=3: [1 0 0; 0 1 0; 0 0 1] == 100010001_2 = 273;
%e A119408 n=4: [1 0 0 0; 0 1 0 0; 0 0 1 0; 0 0 0 1] == 1000010000100001_2 = 33825.
%t A119408 For[n=2,n<=10,Print[n," ",Sum[2^((n+1)(k-1)), {k,1,n}]];n++ ]
%t A119408 Table[FromDigits[Flatten[IdentityMatrix[n]],2],{n,15}] (* _Harvey P. Dale_, Dec 31 2021 *)
%o A119408 (MATLAB) for n = 1:10 bi2de((reshape(eye(n),length(eye(n))^2,1))') end
%o A119408 % _Kyle Stern_, Dec 14 2011
%o A119408 (PARI) a(n)=(2^n*2^(n^2)-1)/(2*2^n-1) \\ _Charles R Greathouse IV_, Jun 09 2015
%Y A119408 Cf. A128889.
%K A119408 nonn,base
%O A119408 1,2
%A A119408 _Lynn R. Purser_, Jul 25 2006