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 A026844 #19 Sep 08 2022 08:44:49 %S A026844 1,10,67,379,1958,9576,45190,208084,941480,4204949,18597694,81635060, %T A026844 356220369,1547066801,6693361973,28868868733,124194904215, %U A026844 533156609953,2284722747583,9776008778375,41777089615201,178338353574365,760586650190997 %N A026844 a(n) = T(2n,n+4), T given by A026725. %C A026844 Column k=9 of triangle A236830. - _Philippe Deléham_, Feb 02 2014 %H A026844 G. C. Greubel, <a href="/A026844/b026844.txt">Table of n, a(n) for n = 4..1000</a> %F A026844 G.f.: (x^4*C(x)^9)/(1-x*C(x)^3) where C(x) is the g.f. of A000108. - _Philippe Deléham_, Feb 02 2014 %F A026844 a(n) ~ phi^(3*n-5) / sqrt(5), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - _Vaclav Kotesovec_, Jul 19 2019 %F A026844 (7719*n+49402)*(n+3)*a(n) +(7719*n^2-1057949*n-1942990)*a(n-1) +4*(-211672*n^2+2076533*n+763807)*a(n-2) +(4326581*n^2-34087269*n+38502298)*a(n-3) +3*(-1940897*n^2+16395555*n-37085206)*a(n-4) -2*(406705*n-1575734)*(2*n-9)*a(n-5)=0. - _R. J. Mathar_, Oct 26 2019 %t A026844 Drop[CoefficientList[Series[(1-Sqrt[1-4x])^9/(64*x^3*(8*x^2-(1-Sqrt[1-4x])^3)), {x,0,40}], x], 4] (* _G. C. Greubel_, Jul 19 2019 *) %o A026844 (PARI) my(x='x+O('x^40)); Vec( (1-sqrt(1-4*x))^9/(64*x^3*(8*x^2 -(1-sqrt(1-4*x))^3)) ) \\ _G. C. Greubel_, Jul 19 2019 %o A026844 (Magma) R<x>:=PowerSeriesRing(Rationals(), 40); Coefficients(R!( (1-Sqrt(1-4*x))^9/(64*x^3*(8*x^2 -(1-Sqrt(1-4*x))^3)) )); // _G. C. Greubel_, Jul 19 2019 %o A026844 (Sage) a=((1-sqrt(1-4*x))^9/(64*x^3*(8*x^2 -(1-sqrt(1-4*x))^3)) ).series(x, 45).coefficients(x, sparse=False); a[4:40] # _G. C. Greubel_, Jul 19 2019 %Y A026844 Cf. A000108, A026725, A236830. %K A026844 nonn %O A026844 4,2 %A A026844 _Clark Kimberling_