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 A276880 #6 Sep 30 2016 13:23:34
%S A276880 1,4,7,12,15,18,23,26,29,34,37,42,45,48,53,56,59,64,67,70,75,78,83,86,
%T A276880 89,94,97,100,105,108,111,116,119,124,127,130,135,138,141,146,149,154,
%U A276880 157,160,165,168,171,176,179,182,187,190,195,198,201,206,209,212
%N A276880 Sums-complement of the Beatty sequence for 1 + sqrt(3).
%C A276880 See A276871 for a definition of sums-complement and guide to related sequences.
%H A276880 <a href="/index/Be#Beatty">Index entries for sequences related to Beatty sequences</a>
%e A276880 The Beatty sequence for 1 + sqrt(3) is A054088 = (0,2,5,8,19,13,16,...), with difference sequence s = A007538 = (2,3,3,2,3,3,3,2,3,3,3,2,3,3,2,...). The sums s(j)+s(j+1)+...+s(k) include (2,3,5,6,8,9,10,11,13,...), with complement (1,4,7,12,15,18,23,...).
%t A276880 z = 500; r = 1 + Sqrt[3]; b = Table[Floor[k*r], {k, 0, z}]; (* A054088 *)
%t A276880 t = Differences[b]; (* A007538 *)
%t A276880 c[k_, n_] := Sum[t[[i]], {i, n, n + k - 1}];
%t A276880 u[k_] := Union[Table[c[k, n], {n, 1, z - k + 1}]];
%t A276880 w = Flatten[Table[u[k], {k, 1, z}]]; Complement[Range[Max[w]], w] (* A276880 *)
%Y A276880 Cf. A054088, A007538, A276871.
%K A276880 nonn,easy
%O A276880 1,2
%A A276880 _Clark Kimberling_, Sep 27 2016