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 A026472 #22 Jan 03 2022 21:37:58
%S A026472 1,2,3,7,13,14,25,26,37,38,49,50,61,62,73,74,85,86,97,98,109,110,121,
%T A026472 122,133,134,145,146,157,158,169,170,181,182,193,194,205,206,217,218,
%U A026472 229,230,241,242,253,254,265,266,277,278,289,290,301,302,313,314
%N A026472 {3, 7} together with the numbers congruent to {1, 2} mod 12.
%C A026472 The old definition of this sequence was "a(n) = least positive integer > a(n-1) and not equal to a(i)+a(j)+a(k) for 1<=i<=j<=k<=n". However, Ralf Stephan observes that this does not fit the terms shown. The present definition (due to Stephan) has been adopted as a temporary solution. - _N. J. A. Sloane_, Nov 24 2004
%C A026472 Regarding the old definition, see Comments at A047239. - _Clark Kimberling_, Oct 09 2019
%H A026472 Clark Kimberling, <a href="/A026472/b026472.txt">Table of n, a(n) for n = 1..10000</a>
%H A026472 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A026472 From _Colin Barker_, Oct 10 2019: (Start)
%F A026472 G.f.: x*(1 + x + 3*x^3 + 5*x^4 - 3*x^5 + 5*x^6) / ((1 - x)^2*(1 + x)).
%F A026472 a(n) = a(n-1) + a(n-2) - a(n-3) for n>6.
%F A026472 a(n) = -(39/2) - (5*(-1)^n)/2 + 6*n for n>4.
%F A026472 (End)
%t A026472 p = {1, 2, 3, 7}; r = 12 Range[200]; Union[p, 1 + r, 2 + r] (* _Clark Kimberling_, Oct 10 2019 *)
%o A026472 (PARI) Vec(x*(1 + x + 3*x^3 + 5*x^4 - 3*x^5 + 5*x^6) / ((1 - x)^2*(1 + x)) + O(x^40)) \\ _Colin Barker_, Oct 20 2019
%Y A026472 Cf. A026476, A026474.
%K A026472 nonn
%O A026472 1,2
%A A026472 _Clark Kimberling_
%E A026472 More terms from _Clark Kimberling_, Oct 10 2019