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 A280295 #26 Dec 31 2020 11:11:15 %S A280295 1,2,9,20,72,144 %N A280295 Smallest number with precipice n. Descending by the main diagonal of the pyramid described in A245092, the height difference between the level a(n) (starting from the top) and the level of the next terrace is equal to n. %C A280295 The structure of the stepped pyramid arises after the 90-degree-zig-zag folding of the diagram of the isosceles triangle A237593. %C A280295 The terraces at the k-th level of the pyramid are also the parts of the symmetric representation of sigma(k), k >= 1. %C A280295 The stepped pyramid is also one of the 3D-quadrants of the stepped pyramid described in A244050. %C A280295 For more information about the precipices see A277437 and A280223. %C A280295 Is this sequence infinite? %H A280295 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/polpyr05.jpg">Perspective view of the pyramid (first 16 steps)</a> %e A280295 a(3) = 9 because descending by the main diagonal of the pyramid, the height difference between the level 9 and the level of the next terrace is equal to 3, and 9 is the smallest number with this property. %Y A280295 Row 1 of A277437. %Y A280295 Cf. A000203, A196020, A235791, A236104, A237591, A237593, A240542, A244050, A245092, A259179, A262626, A276112, A277437, A279286, A279385, A280223. %K A280295 nonn,more %O A280295 1,2 %A A280295 _Omar E. Pol_, Dec 31 2016 %E A280295 a(6) from _Omar E. Pol_, Jan 02 2017