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 A026619 #9 Jun 17 2024 07:02:35
%S A026619 1,5,17,60,217,798,2970,11154,42185,160446,613054,2351440,9048522,
%T A026619 34916300,135059220,523521630,2033066025,7908332190,30807696150,
%U A026619 120173896920,469334610030,1834970026500
%N A026619 a(n) = A026615(2*n-1, n-1).
%H A026619 G. C. Greubel, <a href="/A026619/b026619.txt">Table of n, a(n) for n = 1..1000</a>
%F A026619 From _G. C. Greubel_, Jun 13 2024: (Start)
%F A026619 a(n) = (7*n - 4)*binomial(2*n, n)/(4*(2*n-1)) -(1/2)*[n=1].
%F A026619 G.f.: ( (2 - x) - (2 + x)*sqrt(1-4*x) )/(2*sqrt(1-4*x))
%F A026619 E.g.f.: (1/2)*exp(2*x)*( (2 - x)*BesselI(0, 2*x) + x*BesselI(1, 2*x) ) - (1 + x/2). (End)
%t A026619 Table[(7*n-4)*Binomial[2*n,n]/(4*(2*n-1)) -(1/2)*Boole[n==1], {n,40}] (* _G. C. Greubel_, Jun 13 2024 *)
%o A026619 (Magma) [n eq 1 select 1 else (7*n-4)*(n+1)*Catalan(n)/(4*(2*n-1)): n in [1..40]]; // _G. C. Greubel_, Jun 13 2024
%o A026619 (SageMath) [(7*n-4)*binomial(2*n,n)/(4*(2*n-1)) -(1/2)*int(n==1) for n in range(1,41)] # _G. C. Greubel_, Jun 13 2024
%Y A026619 Cf. A026615, A026616, A026617, A026618, A026620, A026621, A026622.
%Y A026619 Cf. A026623, A026624, A026625, A026956, A026957, A026958, A026959.
%Y A026619 Cf. A026960.
%K A026619 nonn
%O A026619 1,2
%A A026619 _Clark Kimberling_