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 A174381 #6 Jul 03 2021 14:06:50 %S A174381 0,0,4,0,9,36,0,16,16,144,0,25,100,225,400,0,36,9,12,144,900,0,49,196, %T A174381 441,784,1225,1764,0,64,64,576,64,1600,576,3136,0,81,324,81,1296,2025, %U A174381 324,3969,5184,0,100,25,900,400,100,225,4900,1600,8100,0,121,484,1089 %N A174381 Triangle for denominators of half extended Rydberg-Ritz spectrum of the hydrogenic spectra. a(n) is an antidiagonal writing of array in A171522 without first column. %C A174381 Companion to A172157 (numerators). Hence -1/0; -1/0,-3/4; -1/0,-8/9,-5/36; -1/0,-15/16,-3/16,-7/144; -1/0,-24/25,-21/100,-16/225,-9/400; for 1) (-1/0, A005563/A000290(n+1))=A067998(n+1)/A000290 Lyman; 2) -1/0, -3/4, A061037/A061038 Balmer ; 3) -1/0, -8/9, -5/36, A061039/A061040)=A171709(n+3)/ Paschen; 4) (-1/0, -15/16, -3/16, -7/144, A061041/A061042 Brackett; .. . %F A174381 a(n)= 0, (mix 0 or A000004 , n-th row of A120073) %K A174381 nonn,uned %O A174381 0,3 %A A174381 _Paul Curtz_, Mar 17 2010