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 A121622 #36 Dec 31 2023 11:29:36
%S A121622 1,3,5,-9,-119,-597,-2035,-4449,-239,56403,341525,1315911,3455641,
%T A121622 3627003,-23161315,-186118929,-815616479,-2474152797,-4241902555,
%U A121622 6712571031,95420159401,485257533003,1671083125805,3718150825791,584824319281
%N A121622 Real part of (3 + 2i)^n.
%C A121622 Companion sequence A121621 is real((2 + 3i)^n).
%H A121622 Michael De Vlieger, <a href="/A121622/b121622.txt">Table of n, a(n) for n = 0..500</a>
%H A121622 Beata Bajorska-Harapińska, Barbara Smoleń, and Roman Wituła, <a href="https://doi.org/10.1007/s00006-019-0969-9">On Quaternion Equivalents for Quasi-Fibonacci Numbers, Shortly Quaternaccis</a>, Advances in Applied Clifford Algebras (2019) Vol. 29, 54.
%H A121622 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (6,-13).
%F A121622 a(n) = real((3 + 2i)^n).
%F A121622 a(n) = 6*a(n-1) - 13*a(n-2).
%F A121622 G.f.: ( 1-3*x ) / ( 1-6*x+13*x^2 ). - _R. J. Mathar_, Aug 12 2012
%F A121622 E.g.f.: exp(3*x)*cos(2*x). - _Sergei N. Gladkovskii_, Jan 20 2014
%e A121622 a(5) = -597 since (3 + 2i)^5 = (-597 + 122i).
%e A121622 a(5) = -597 = 6*(-119) - 13*(-9) = 6*a(5) -13*a(4).
%t A121622 f[n_] := Re[(3 + 2I)^n]; Table[f[n], {n, 0, 24}] (* _Robert G. Wilson v_, Aug 17 2006 *)
%t A121622 LinearRecurrence[{6,-13},{1,3},30] (* _Harvey P. Dale_, Apr 24 2017 *)
%o A121622 (PARI) a(n) = real((3 + 2*I)^n); \\ _Michel Marcus_, Jun 12 2021
%Y A121622 Cf. A121621.
%Y A121622 Cf. A193410, A066771.
%K A121622 sign,easy
%O A121622 0,2
%A A121622 _Gary W. Adamson_ and Nick Williams, Aug 10 2006
%E A121622 More terms from _Robert G. Wilson v_, Aug 17 2006