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 A093423 #17 Sep 08 2022 08:45:13
%S A093423 1,1,3,1,5,1,1,7,3,5,1,9,1,7,1,1,11,1,1,1,7,1,13,3,11,5,3,1,1,15,1,13,
%T A093423 1,11,1,1,1,17,1,5,1,13,1,11,1,1,19,3,17,1,1,7,13,1,11,1,21,1,19,1,17,
%U A093423 1,1,1,13,1,1,23,1,7,5,19,1,17,1,1,1,13
%N A093423 Consider the triangle whose first part is shown as an example in the entry A093422. If the n-th term of the triangle read by rows is a fraction then a(n) is the denominator of the fraction, otherwise a(n)=1.
%H A093423 G. C. Greubel, <a href="/A093423/b093423.txt">Rows n=1..100 of triangle, flattened</a>
%F A093423 A093422(n,m)/A093423(n,m) = 2*binomial(n,m)*(m-1)!/(2*n-m+1) for 2 <= m < n. A093422(n,1)/A093423(n,1)= n. - _R. J. Mathar_, Apr 28 2007
%e A093423 Triangle begins:
%e A093423 1;
%e A093423 1, 3;
%e A093423 1, 5, 1;
%e A093423 1, 7, 3, 5;
%e A093423 1, 9, 1, 7, 1;
%e A093423 1, 11, 1, 1, 1, 7;
%e A093423 1, 13, 3, 11, 5, 3, 1;
%e A093423 1, 15, 1, 13, 1, 11, 1, 1;
%e A093423 ...
%p A093423 A09342x := proc(n,m) local a,i,N,D ; N := n ; if m = 1 then D := 1 ; else D := n ; end ; for i from 1 to m-1 do N := N*(n-i) ; D := D+n-i ; od ; simplify(N/D) ; end: A093423 := proc(n,m) denom(A09342x(n,m)) ; end: for n from 1 to 12 do for m from 1 to n do printf("%d, ",A093423(n,m)) ; od ; od ; # _R. J. Mathar_, Apr 28 2007
%t A093423 Table[Denominator[2*Binomial[n,k]*(k-1)!/(2*n-k+1)], {n,1,30}, {k,1,n}]//Flatten (* _G. C. Greubel_, Sep 01 2018 *)
%o A093423 (PARI) for(n=1,10, for(k=1,n, print1(denominator(2*binomial(n,k)*(k-1)!/(2*n-k+1)), ", "))) \\ _G. C. Greubel_, Sep 01 2018
%o A093423 (Magma) /* as a triangle */ [[Denominator(2*Binomial(n,k)*Factorial(k-1)/(2*n-k+1)): k in [1..n]]: n in [1..30]]; // _G. C. Greubel_, Sep 01 2018
%Y A093423 Cf. A093412, A093413, A093414, A093415, A093417, A093418, A093419, A093420, A093421, A093422.
%K A093423 nonn,tabl,frac
%O A093423 1,3
%A A093423 _Amarnath Murthy_, Mar 30 2004
%E A093423 More terms from _R. J. Mathar_, Apr 28 2007
%E A093423 Better definition from _Omar E. Pol_, Jan 10 2009