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 A376899 #21 Nov 03 2024 19:25:53 %S A376899 160,24,27,8,0,0,0 %N A376899 Total number of ways a triangle of order n can be completely surrounded by a specific pentiamond. %C A376899 The coronal expansion number is defined to be the number of expansions the central host frame can undergo and still have a corona formed by the coronal tile. The coronal expansion number is 4 for this sequence. See the links section for an example of a pseudo-triangle as the central host frame that has a coronal expansion number of 7. _Craig Knecht_, Oct 31 2024 %H A376899 Craig Knecht, <a href="/A376899/a376899_2.png">Pseudo triangle with a coronal expansion number of 7.</a> %H A376899 Craig Knecht, <a href="/A376899/a376899.png">The 160 ways this pentiamond can surround a T1 triangle</a>. %H A376899 Craig Knecht, <a href="/A376899/a376899_1.png">T2, T3, and T4 surrounded by this pentiamond</a>. %K A376899 nonn,more %O A376899 1,1 %A A376899 _Craig Knecht_, Oct 08 2024