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 A004172 #26 Feb 16 2025 08:32:28
%S A004172 1,0,-1,1,0,1,0,-2,1,0,-3,0,5,0,-3,1,0,17,0,-28,0,14,0,-4,1,0,-155,0,
%T A004172 255,0,-126,0,30,0,-5,1,0,2073,0,-3410,0,1683,0,-396,0,55,0,-6,1,0,
%U A004172 -38227,0,62881,0,-31031,0,7293,0,-1001,0,91,0,-7,1,0,929569,0
%N A004172 Triangle of coefficients of Euler polynomials E_2n(x) (exponents in increasing order).
%D A004172 M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 809.
%H A004172 T. D. Noe, <a href="/A004172/b004172.txt">Rows n = 0..50 of triangle, flattened</a>
%H A004172 M. Abramowitz and I. A. Stegun, eds., <a href="http://www.convertit.com/Go/ConvertIt/Reference/AMS55.ASP">Handbook of Mathematical Functions</a>, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
%H A004172 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EulerPolynomial.html">Euler Polynomial</a>.
%t A004172 Flatten[Table[CoefficientList[EulerE[2n, x], x], {n, 0, 8}]] (* _Jean-François Alcover_, Jul 21 2011 *)
%Y A004172 Cf. A060083.
%K A004172 sign,tabl,nice
%O A004172 0,8
%A A004172 _N. J. A. Sloane_