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 A098821 #20 Feb 16 2025 08:32:54
%S A098821 4,4,5,9,21,53,133,325,773,1797,4101,9221,20485,45061,98309,212997,
%T A098821 458757,983045,2097157,4456453,9437189,19922949,41943045,88080389,
%U A098821 184549381,385875973,805306373,1677721605,3489660933,7247757317
%N A098821 a(n) = (n-2) * 2^(n-1) + 5.
%D A098821 G. H. Hardy and J. E. Littlewood, "Some problems of partitio numerorum (VI): Further researches in Waring's Problem", Math. Z. vol. 23, 1-37, (1925)
%D A098821 T. D. Wooley, "Large improvements in Waring's Problem", Ann. Math. vol. 135, 131-164 (1992)
%H A098821 Eric Weisstein, <a href="https://mathworld.wolfram.com/WaringsProblem.html">Waring's problem</a>
%H A098821 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5, -8, 4).
%F A098821 From _Colin Barker_, Jan 28 2012: (Start)
%F A098821 G.f.: (4-16*x+17*x^2)/(1-5*x+8*x^2-4*x^3).
%F A098821 a(n)=5*a(n-1)-8*a(n-2)+4*a(n-3). (End)
%e A098821 a(5) = 3*2^4 + 5 = 53.
%t A098821 Table[(n - 2)*2^(n - 1) + 5, {n, 0, 30}] (* _Stefan Steinerberger_, Mar 06 2006 *)
%t A098821 LinearRecurrence[{5,-8,4},{4,4,5},40] (* _Harvey P. Dale_, Feb 22 2013 *)
%o A098821 (PARI) a(n)=(n-2)<<(n-1)+5 \\ _Charles R Greathouse IV_, Jul 23 2015
%Y A098821 Cf. A018889, A002804.
%K A098821 nonn,easy
%O A098821 0,1
%A A098821 _Parthasarathy Nambi_, Oct 08 2004
%E A098821 More terms from _Stefan Steinerberger_, Mar 06 2006