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 A028322 #17 Jul 02 2025 16:01:56
%S A028322 1,5,12,38,130,462,1680,6204,23166,87230,330616,1259700,4820452,
%T A028322 18513068,71318400,275467320,1066432950,4136847390,16075953960,
%U A028322 62570669700,243882320220,951797460900,3718872587040,14545727618760
%N A028322 Central elements in the 5-Pascal triangle A028313.
%H A028322 G. C. Greubel, <a href="/A028322/b028322.txt">Table of n, a(n) for n = 0..1000</a>
%F A028322 G.f.: (1 + 3*x)/sqrt(1-4*x). - _Vladeta Jovovic_, Jan 08 2004
%F A028322 a(n) = A000984(n) + 3*A000984(n-1). - _R. J. Mathar_, Dec 15 2015
%F A028322 a(n) = (n+1)*(7*n-2)*A000108(n)/(2*(2*n-1)). - _G. C. Greubel_, Jan 05 2024
%t A028322 Table[(n+1)*(7*n-2)*CatalanNumber[n]/(2*(2*n-1)), {n,0,40}] (* _G. C. Greubel_, Jan 05 2024 *)
%o A028322 (Magma) [(n+1)*(7*n-2)*Catalan(n)/(2*(2*n-1)): n in [0..40]]; // _G. C. Greubel_, Jan 05 2024
%o A028322 (SageMath) [(7*n-2)*binomial(2*n,n)/(2*(2*n-1)) for n in range(41)] # _G. C. Greubel_, Jan 05 2024
%Y A028322 Cf. A000108, A000984, A028313.
%K A028322 nonn,easy
%O A028322 0,2
%A A028322 _Mohammad K. Azarian_
%E A028322 More terms from _James Sellers_