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 A183420 #11 Mar 30 2012 18:57:12 %S A183420 2,14,4,254,18,34,6,65534,270,398,22,1294,40,62,9,4294967294,65790, %T A183420 73982,286,159998,418,574,27,1679614,1330,1762,46,4094,70,119,12 %N A183420 First of two complementary trees generated by the squares; the other tree is A183421. %C A183420 Begin with the main tree A183169 generated by the squares: %C A183420 ......................1 %C A183420 ......................2 %C A183420 ...........4.....................3 %C A183420 .......16.......6...........9..........5 %C A183420 ...256...20...36..8......81...12....25...7 %C A183420 Every n>2 is in the subtree from 4 or the subtree from 3. Therefore, on subtracting 2 from all entries of those subtrees, we obtain complementary trees: A183420 and A183421. %F A183420 See the formulas at A183169 and A183422. %e A183420 First three levels: %e A183420 ..................2 %e A183420 .............14.........4 %e A183420 ..........254...18....34...6 %Y A183420 Cf. A183169, A183420, A183421, A183422, A183231 (analogous trees generated by the triangular numbers). %K A183420 nonn,tabf %O A183420 1,1 %A A183420 _Clark Kimberling_, Jan 04 2011