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 A135417 #6 May 05 2023 09:20:51 %S A135417 1,0,8,56,252,784,1792,3108,4166,4352,3544,2232,1068,376,92,14,1 %N A135417 Number of mountain numbers (see A134941) with n digits. %C A135417 The total number is 21846. %e A135417 Contribution from _Reinhard Zumkeller_, May 25 2010: (Start) %e A135417 a(1) = A178334(9) = 1; %e A135417 a(2) = A178334(99) - A178334(9) = 1 - 1 = 0; %e A135417 a(3) = A178334(999) - A178334(99) = 9 - 1 = 8; %e A135417 a(4) = A178334(9999) - A178334(999) = 65 - 9 = 56. (End) %K A135417 base,nonn,fini,full %O A135417 1,3 %A A135417 Suggested by _Jonathan Vos Post_, Nov 24 2007 and computed by _Hans Havermann_ and _Joshua Zucker_, Nov 25 2007