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 A274646 #13 Dec 15 2016 18:10:40 %S A274646 1,70,26599,29609650,72574079902,332014782982540,2545213373338499072, %T A274646 30302687687176712355840,529556871638491591748878336, %U A274646 13004213964445490176628310933504,433440210434110194677894532074307584 %N A274646 Number of linear extensions of the one-level grid poset G[(3^n), (0^(n-1)), (0^(n-1))]. %C A274646 The definition of a one-level grid poset can be found in the Pan links. The number of linear extensions of one-level grid poset G[(0^n), (0^(n-1)), (0^(n-1))] is given by Catalan number A000108(n), the number of linear extensions of the one-level grid poset G[(1^n), (0^(n-1)), (0^(n-1))] is given by A274644(n) and number of linear extensions of the one-level grid poset G[(2^n), (0^(n-1)), (0^(n-1))] is given by A274645(n). %H A274646 Ran Pan, <a href="http://www.math.ucsd.edu/~projectp/problems/p1.html">Problem 1</a>, Project P. %H A274646 Ran Pan, <a href="http://www.math.ucsd.edu/~projectp/problems/solutions/OneLevelGridPoset.pdf">Algorithmic Solution to Problem 1 (and linear extensions of general one-level grid-like posets)</a>, Project P. %Y A274646 Cf. A000108, A274644, A274645. %K A274646 nonn %O A274646 1,2 %A A274646 _Ran Pan_, Jun 30 2016