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 A082143 #19 Jan 16 2024 01:39:49
%S A082143 1,3,20,140,1008,7392,54912,411840,3111680,23648768,180590592,
%T A082143 1384527872,10650214400,82158796800,635361361920,4924050554880,
%U A082143 38233804308480,297374033510400,2316387208396800,18067820225495040,141101072237199360,1103153837490831360
%N A082143 First subdiagonal of number array A082137.
%H A082143 Reinhard Zumkeller, <a href="/A082143/b082143.txt">Table of n, a(n) for n = 0..1000</a>
%F A082143 a(n) = (2^(n-1) + 0^n/2)*C(2n+1, n).
%F A082143 Conjecture: (n+1)*a(n) +4*(-2*n-1)*a(n-1)=0. - _R. J. Mathar_, Oct 19 2014
%F A082143 From _Reinhard Zumkeller_, Jan 15 2015: (Start)
%F A082143 a(n) = A000079(n-1) * A001700(n), for n > 0.
%F A082143 a(n) = A069720(n+1)/2. (End)
%F A082143 From _Amiram Eldar_, Jan 16 2024: (Start)
%F A082143 Sum_{n>=0} 1/a(n) = 64*arcsin(1/(2*sqrt(2)))/(7*sqrt(7)) + 1/7.
%F A082143 Sum_{n>=0} (-1)^n/a(n) = 32*log(2)/27 - 1/9. (End)
%e A082143 a(0)=(2^(-1)+(0^0)/2)C(1,0)=2*(1/2)=1 (use 0^0=1).
%t A082143 Join[{1}, Table[2^(n-1)* Binomial[2*n+1,n], {n,1,30}]] (* _G. C. Greubel_, Feb 05 2018 *)
%o A082143 (Haskell)
%o A082143 a082143 0 = 1
%o A082143 a082143 n = (a000079 $ n - 1) * (a001700 n)
%o A082143 -- _Reinhard Zumkeller_, Jan 15 2015
%o A082143 (PARI) for(n=0,30, print1((2^(n-1) + 0^n/2)*Binomial(2*n+1,n), ", ")) \\ _G. C. Greubel_, Feb 05 2018
%o A082143 (Magma) [(2^(n-1) + 0^n/2)*Binomial(2*n+1,n): n in [0..30]]; // _G. C. Greubel_, Feb 05 2018
%Y A082143 Cf. A069723, A082144, A082145.
%Y A082143 Cf. A000079, A001700, A069720.
%K A082143 easy,nonn
%O A082143 0,2
%A A082143 _Paul Barry_, Apr 06 2003