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 A355755 #19 Apr 26 2024 07:58:17 %S A355755 1,0,1,0,1,1,0,1,2,2,1,0,1,4,7,6,2,1,0,1,6,22,36,27,13,4,2,1,0,1,9,53, %T A355755 161,242,209,111,43,17,5,1,1,0,1,12,114,611,1766,2903,2793,1723,773, %U A355755 284,86,36,9,3,2,1,0,1,16,221,1987,10517,33078,60639,67379,48035,24628,9715,3349,1049,310,105,36,9,4,1,1 %N A355755 Irregular triangle read by rows: T(n,k) is the number of unlabeled connected n-node graphs with intersection number (or edge clique cover number) k; n >= 1, 0 <= k <= floor(n^2/4). %H A355755 Eric W. Weisstein, <a href="/A355755/b355755.txt">Table of n, a(n) for n = 1..108</a> %H A355755 Paul Erdős, A. W. Goodman, and Louis Pósa, <a href="https://doi.org/10.4153%2FCJM-1966-014-3">The representation of a graph by set intersections</a>, Canadian Journal of Mathematics 18 (1966), 106-112. %H A355755 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IntersectionNumber.html">Intersection Number</a> %H A355755 Wikipedia, <a href="https://en.wikipedia.org/wiki/Intersection_number_(graph_theory)">Intersection number</a> %F A355755 T(n,0) = 0 if n > 1. %F A355755 T(n,1) = 1. %F A355755 T(n,2) = floor((n-1)^2/4) = A002620(n-1). %e A355755 Triangle begins: %e A355755 n\k | 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 %e A355755 ----+-------------------------------------------------------------- %e A355755 1 | 1 %e A355755 2 | 0 1 %e A355755 3 | 0 1 1 %e A355755 4 | 0 1 2 2 1 %e A355755 5 | 0 1 4 7 6 2 1 %e A355755 6 | 0 1 6 22 36 27 13 4 2 1 %e A355755 7 | 0 1 9 53 161 242 209 111 43 17 5 1 1 %e A355755 8 | 0 1 12 114 611 1766 2903 2793 1723 773 284 86 36 9 3 2 1 %Y A355755 Cf. A001349 (row sums), A002620, A355754. %K A355755 nonn,tabf %O A355755 1,9 %A A355755 _Pontus von Brömssen_, Jul 16 2022