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 A357283 #4 Oct 01 2022 19:33:39
%S A357283 0,0,0,0,2,8,26,68,166,376,826,1756,3678,7584,15522,31524,63782,
%T A357283 128552,258602,519212,1041454,2086960,4180018,8368180,16748598,
%U A357283 33513528,67051578,134135868,268320830,536707136,1073512514,2147156036,4294508614,8589279304
%N A357283 a(n) = number of subsets S of {1,2,...,n} having more than 1 element such that (sum of least two elements of S) < max(S).
%H A357283 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (4,-3,-6,10,-4).
%F A357283 a(n) = 4*a(n-1) - 3*a(n-2) - 6*a(n-3) + 10*a(n-4) - 4*a(n-5).
%F A357283 G.f.: (2 x^4)/((-1 + x)^2 (1 - 2 x - 2 x^2 + 4 x^3)).
%e A357283 The 2 relevant subsets of {1,2,3,4} and {1,2,4} and {1,2,3,4}.
%t A357283 s[n_] := s[n] = Select[Subsets[Range[n]], Length[#] >= 2 &]; (* note size >=2 *)
%t A357283 a[n_] := Select[s[n], #[[2]] + #[[1]] < #[[-1]] &]
%t A357283 Table[Length[a[n]], {n, 0, 18}]
%Y A357283 Cf. A357284.
%K A357283 nonn,easy
%O A357283 0,5
%A A357283 _Clark Kimberling_, Sep 27 2022