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 A145452 #21 Dec 28 2023 19:38:05
%S A145452 1,197,1529074009,715015595589726925478809323773,
%T A145452 73109958817558064847374518951460268418149511794461927024546978118655493358310911623870212081
%N A145452 a(n) = (1/(10*sqrt(2)))*((1 + sqrt(2))^(3^n) - (1 - sqrt(2))^(3^n)).
%H A145452 G. C. Greubel, <a href="/A145452/b145452.txt">Table of n, a(n) for n = 1..7</a>
%F A145452 a(n) = (1/(10*sqrt(2)))*((1 + sqrt(2))^(3^n) - (1 - sqrt(2))^(3^n)).
%F A145452 a(n+1) = 200*a(n)^3 - 3*a(n), a(1) = 1.
%F A145452 a(n) = A000129(3^n)/5 . - _R. J. Mathar_, Jan 18 2021
%t A145452 Table[Simplify[Expand[(1/(10Sqrt[2]))((1+Sqrt[2])^(3^n) + (1-Sqrt[2])^(3^n))]], {n,5}]
%t A145452 Fibonacci[3^Range[6], 2]/5 (* _G. C. Greubel_, Mar 25 2022 *)
%o A145452 (Magma) [Evaluate(DicksonSecond(3^n -1, -1), 2)/5: n in [1..6]]; // _G. C. Greubel_, Mar 25 2022
%o A145452 (Sage) [lucas_number1(3^n,2,-1)/5 for n in (1..6)] # _G. C. Greubel_, Mar 25 2022
%Y A145452 Cf. A000129, A006266, A145451.
%K A145452 nonn
%O A145452 1,2
%A A145452 _Artur Jasinski_, Oct 10 2008
%E A145452 Offset corrected by _R. J. Mathar_, Jan 18 2021