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 A018037 #11 Sep 08 2022 08:44:44
%S A018037 1,3,8,21,58,160,441,1217,3357,9261,25550,70492,194481,536558,1480324,
%T A018037 4084101,11267725,31086799,85766121,236622225,652822777,1801088541,
%U A018037 4969066720,13709278307,37822859361,104350401111,287894844440,794280046581,2191358423329
%N A018037 Powers of cube root of 21 rounded to nearest integer.
%H A018037 Vincenzo Librandi, <a href="/A018037/b018037.txt">Table of n, a(n) for n = 0..200</a>
%t A018037 Table[Round[21^(n/3)], {n, 0, 40}] (* _Vincenzo Librandi_, Jan 08 2014 *)
%o A018037 (Magma) [Round(21^(n/3)): n in [0..40]]; // _Vincenzo Librandi_, Jan 08 2014
%Y A018037 Cf. powers of cube root of k rounded up: A017980 (k=2), A017983 (k=3), A017986 (k=4), A017989 (k=5), A017992 (k=6), A017995 (k=7), A018001 (k=9), A018004 (k=10), A018007 (k=11), A018010 (k=12), A018013 (k=13), A018016 (k=14), A018019 (k=15), A018022 (k=16), A018025 (k=17), A018028 (k=18), A018031 (k=19), A018034 (k=20), this sequence (k=21), A018040 (k=22), A018043 (k=23), A018046 (k=24).
%K A018037 nonn
%O A018037 0,2
%A A018037 _N. J. A. Sloane_
%E A018037 More terms from _Vincenzo Librandi_, Jan 08 2014