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 A074081 #18 Jun 03 2025 02:55:00
%S A074081 4,-1,3,-7,15,-26,51,-99,191,-367,708,-1365,2631,-5071,9775,-18842,
%T A074081 36319,-70007,134943,-260111,501380,-966441,1862875,-3590807,6921503,
%U A074081 -13341626,25716811,-49570747,95550687,-184179871,355018116,-684319421,1319068095,-2542585503,4900991135
%N A074081 Sum of determinants of 3rd-order principal minors of powers of inverse of tetramatrix ((1,1,0,0),(1,0,1,0),(1,0,0,1),(1,0,0,0)).
%H A074081 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-1,1,-1,1).
%F A074081 a(n) = (-1)^n*T(n), where T(n) are the generalized tetranacci numbers A073817.
%F A074081 a(n) = -a(n-1)+a(n-2)-a(n-3)+a(n-4), a(0)=4, a(1)=-1, a(2)=3, a(3)=-7.
%F A074081 G.f.: (4+3x-2x^2+x^3)/(1+x-x^2+x^3-x^4).
%t A074081 CoefficientList[Series[(4+3*x-2*x^2+x^3)/(1+x-x^2+x^3-x^4), {x, 0, 40}], x]
%Y A074081 Cf. A073817.
%K A074081 easy,sign
%O A074081 0,1
%A A074081 Mario Catalani (mario.catalani(AT)unito.it), Aug 19 2002