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 A006998 M0990 #24 Jun 10 2021 16:02:41 %S A006998 0,1,2,4,6,8,12,14,16,24,26,28,32,40,48,52,54,56,64,72,80,96,100,104, %T A006998 108,110,112,128,136,144,160,176,192,200,204,208,216,218,220,224,240, %U A006998 256,272,280,288,320,336,352,384,392,400,408,412,416,432,434,436,440 %N A006998 Partitioning integers to avoid arithmetic progressions of length 3. %D A006998 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006998 Rémy Sigrist, <a href="/A006998/b006998.txt">Table of n, a(n) for n = 0..10000</a> %H A006998 Joseph Gerver, James Propp and Jamie Simpson, <a href="https://dx.doi.org/10.1090/S0002-9939-1988-0929018-1">Greedily partitioning the natural numbers into sets free of arithmetic progressions</a> Proc. Amer. Math. Soc., Vol. 102, No. 3 (1988), 765-772. %H A006998 James Propp and N. J. A. Sloane, <a href="/A006997/a006997.pdf">Email, March 1994</a> %F A006998 a(n) = a([ 2n/3 ]) + a([ (2n+1)/3 ]). %o A006998 (PARI) for (n=1, #a=vector(58), print1 (a[n]=if (n<=2, n-1, a[1+((2*n-2)\3)]+a[1+((2*n-1)\3)])", ")) \\ _Rémy Sigrist_, Jun 10 2021 %Y A006998 Cf. A006997, A006999. %K A006998 nonn,look %O A006998 0,3 %A A006998 _N. J. A. Sloane_, _James Propp_ %E A006998 More terms from _Rémy Sigrist_, Jun 10 2021