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 A007087 M1035 #13 Nov 07 2017 18:20:36 %S A007087 1,2,4,7,10,12,16,17,32,36,42,57,72,73,98,102,104,129,159,164,174,189, %T A007087 199,221,224,255,286,287,347,372,378,403,428,443,444,469,494,529,560, %U A007087 586 %N A007087 Next term is uniquely the sum of 3 earlier terms. %D A007087 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %D A007087 M. C. Wunderlich, The improbable behavior of Ulam's summation sequence, pp. 249-257 of A. O. L. Atkin and B. J. Birch, editors, Computers in Number Theory. Academic Press, NY, 1971. %H A007087 R. G. Wilson, V, <a href="/A002858/a002858_3.pdf">Letter to N. J. A. Sloane, Sep. 1992</a> %K A007087 nonn %O A007087 1,2 %A A007087 _N. J. A. Sloane_, _Robert G. Wilson v_