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 A181345 #11 Feb 23 2020 14:58:54
%S A181345 0,0,0,1,2,12,87,662,5611,51141,509277,5504398,64122940,800741192,
%T A181345 10673478573,151323048909
%N A181345 Number of n X n matrices over {0,1} with rows and columns summing to 3, rows and columns sorted (>) by value.
%H A181345 Bert Dobbelaere, <a href="/A181345/a181345.pdf">Illustration of initial terms</a>
%e A181345 n=4: {1110,1101,1011,0111} is the only matrix where each row (column) - read as a binary number - is larger than the previous one, so a(4)=1.
%Y A181345 Cf. A000512, A001501, A181344.
%K A181345 hard,nonn
%O A181345 1,5
%A A181345 Michael Steyer (m.steyer(AT)osram.de), Oct 18 2010
%E A181345 Offset corrected and a(10)-a(16) from _Bert Dobbelaere_, Feb 23 2020