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 A026474 #37 Feb 16 2025 08:32:35
%S A026474 1,2,4,8,15,22,29,36,43,50,57,64,71,78,85,92,99,106,113,120,127,134,
%T A026474 141,148,155,162,169,176,183,190,197,204,211,218,225,232,239,246,253,
%U A026474 260,267,274,281,288,295,302,309,316,323,330,337,344,351,358,365,372
%N A026474 a(n) = least positive integer > a(n-1) and not equal to a(i)+a(j) or a(i)+a(j)+a(k) for 1<=i<j<k<n (a 3-Stohr sequence).
%C A026474 All h-Stohr sequences have formula: h terms 1,2,..,2^(n-1),..,2^(h-1) and then continue (2^h-1)(n-h)+1. - _Henry Bottomley_, Feb 04 2000
%H A026474 Vincenzo Librandi, <a href="/A026474/b026474.txt">Table of n, a(n) for n = 1..1000</a>
%H A026474 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/StoehrSequence.html">Stoehr Sequence.</a>
%H A026474 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A026474 Starts 1, 2, 4 then the numbers 7*(n-3)+1.
%F A026474 a(n) = 7*n-20 for n>3. a(n) = 2*a(n-1)-a(n-2) for n>5. G.f.: x*(1+x^2+2*x^3+3*x^4)/(1-x)^2. - _Colin Barker_, Sep 19 2012
%t A026474 Join[{1,2,4,8},Range[15,500,7]] (* _Vladimir Joseph Stephan Orlovsky_, Jan 27 2012 *)
%t A026474 CoefficientList[Series[(1 + x^2 + 2 x^3 + 3 x^4)/(1 - x)^2, {x, 0, 60}], x] (* _Vincenzo Librandi_, Oct 18 2013 *)
%t A026474 LinearRecurrence[{2,-1},{1,2,4,8,15},60] (* _Harvey P. Dale_, May 14 2018 *)
%o A026474 (Magma) [1,2,4] cat [7*n+1: n in [1..60]]; // _Vincenzo Librandi_, Oct 18 2013
%o A026474 (PARI) a(n)=if(n>3,7*n-20,2^(n-1)) \\ _Charles R Greathouse IV_, Sep 17 2015
%Y A026474 Cf. A026472, A026476, A033627, A051039, A051040.
%K A026474 nonn,easy
%O A026474 1,2
%A A026474 _Clark Kimberling_
%E A026474 More terms from _Eric W. Weisstein_