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 A056207 #16 Mar 24 2021 11:47:05 %S A056207 3,24,675,458328,210066388899,44127887745906175987800, %T A056207 1947270476915296449559703445493848930452791203, %U A056207 3791862310265926082868235028027893277370233152247388584761734150717768254410341175325352024 %N A056207 Number of binary trees of height <= n. %D A056207 Todd K. Moon, "Enumerations of binary trees, types of trees and the number of reversible variable length codes," submitted to Discrete Applied Mathematics, 2000. %H A056207 <a href="/index/Aa#AHSL">Index entries for sequences of form a(n+1)=a(n)^2 + ...</a> %F A056207 a(n) = d(n) + a(n-1), d(n) = A001699(n) is the number of binary trees of depth exactly n. %F A056207 a(n) = A003095(n+2) - 2 = A004019(n+1) - 1 = a(n-1)^2 + 4*a(n-1) + 3. %o A056207 (Python) %o A056207 from itertools import accumulate %o A056207 def f(anm1, _): return anm1**2 + 4*anm1 + 3 %o A056207 def aupton(terms): return list(accumulate([3]*terms, f)) %o A056207 print(aupton(8)) # _Michael S. Branicky_, Mar 24 2021 %Y A056207 Cf. A001699, A002449, A003095. %K A056207 easy,nonn %O A056207 1,1 %A A056207 Todd K. Moon (Todd.Moon(AT)ece.usu.edu), Aug 02 2000 %E A056207 More terms from _Henry Bottomley_, Jul 09 2001