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 A321133 #37 Mar 11 2023 08:24:54
%S A321133 -1,23,59,407,1811,9503,46619,234887,1170851,5861423,29292779,
%T A321133 146492567,732405491,3662142143,18310481339,91552865447,457763409731,
%U A321133 2288818883663,11444090748299,57220461081527,286102290727571,1430511482997983,7152557356269659,35762786898788807,178813934259063011
%N A321133 a(n) = 3*a(n-1) + 10*a(n-2), n >= 2; a(0)=-1, a(1)=23.
%H A321133 Harvey P. Dale, <a href="/A321133/b321133.txt">Table of n, a(n) for n = 0..1000</a>
%H A321133 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,10).
%F A321133 a(n) = 3*5^n - 4*(-2)^n.
%F A321133 G.f.: (-1+26*x)/((1-5*x)*(1+2*x)).
%F A321133 a(n) == 7*A320469(n)*A224473(n) mod 10^n.
%F A321133 a(n)*A224473(n) == 7*A320469(n) mod 10^n.
%t A321133 LinearRecurrence[{3,10},{-1,23},30] (* _Harvey P. Dale_, Mar 11 2023 *)
%o A321133 (PARI) {a(n) = 3*5^n-4*(-2)^n}
%o A321133 (PARI) N=40; x='x+O('x^N); Vec((-1+26*x)/((1-5*x)*(1+2*x)))
%Y A321133 Cf. A053428, A224473 (trimorphic number), A320468, A320469.
%K A321133 sign,easy
%O A321133 0,2
%A A321133 _Seiichi Manyama_, Aug 27 2019