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 A178474 #7 Jul 20 2019 08:03:57 %S A178474 1,2,1,2,1,1,2,2,2,1,2,1,1,1,1,2,2,1,1,2,1,2,1,2,1,2,1,1,2,2,2,2,2,2, %T A178474 2,1,2,1,1,1,1,1,1,1,1,2,2,1,1,1,1,1,1,2,1,2,1,2,1,1,1,1,1,2,1,1,2,2, %U A178474 2,2,1,1,1,1,2,2,2,1,2,1,1,1,2,1,1,1,2,1,1,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,1 %N A178474 Triangle T(n,m) read by rows: the denominator of the coefficient [x^m] of the inverse Euler polynomial E^{-1}(n,x), 0<=m<=n. %C A178474 As commented in A178395, the triangle of fractions of coefficients of the inverse Euler polynomials starts in row n=0 with column 0<=m<=n as: %C A178474 1; %C A178474 1/2,1; %C A178474 1/2,1,1; %C A178474 1/2,3/2,3/2,1; %C A178474 1/2,2,3,2,1; %C A178474 1/2,5/2,5,5,5/2,1; %C A178474 1/2,3,15/2,10,15/2,3,1; %C A178474 1/2,7/2,21/2,35/2,35/2,21/2,7/2,1; %C A178474 1/2,4,14,28,35,28,14,4,1; %C A178474 1/2,9/2,18,42,63,63,42,18,9/2,1; %C A178474 1/2,5,45/2,60,105,126,105,60,45/2,5,1; %C A178474 Partial row sums (skipping the left column) in this triangle are sum_{m>=1} [x^m] E^{-1}(n,x) = 2^(n-1). %C A178474 T(n,m) is the denominator of the fraction in row n and column m. %e A178474 1; %e A178474 2,1; %e A178474 2,1,1; %e A178474 2,2,2,1; %e A178474 2,1,1,1,1; %e A178474 2,2,1,1,2,1; %e A178474 2,1,2,1,2,1,1; %e A178474 2,2,2,2,2,2,2,1; %e A178474 2,1,1,1,1,1,1,1,1; %e A178474 2,2,1,1,1,1,1,1,2,1; %e A178474 2,1,2,1,1,1,1,1,2,1,1; %e A178474 2,2,2,2,1,1,1,1,2,2,2,1; %e A178474 2,1,1,1,2,1,1,1,2,1,1,1,1; %e A178474 2,2,1,1,2,2,1,1,2,2,1,1,2,1; %e A178474 2,1,2,1,2,1,2,1,2,1,2,1,2,1,1; %t A178474 (* The function RiordanArray is defined in A256893. *) %t A178474 rows = 15; %t A178474 R = RiordanArray[(1 + E^#)/2&, #&, rows, True]; %t A178474 R // Flatten // Denominator (* _Jean-François Alcover_, Jul 20 2019 *) %Y A178474 Cf. A178395 (numerators) %K A178474 nonn,tabl,frac %O A178474 0,2 %A A178474 _Paul Curtz_, May 28 2010