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 A067422 #11 Jun 29 2023 10:42:47 %S A067422 1,9,189,3969,83349,1750329,36756909,771895089,16209796869, %T A067422 340405734249,7148520419229,150118928803809,3152497504879989, %U A067422 66202447602479769,1390251399652075149,29195279392693578129 %N A067422 Seventh column of triangle A067417. %H A067422 Vincenzo Librandi, <a href="/A067422/b067422.txt">Table of n, a(n) for n = 0..700</a> %H A067422 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (21). %F A067422 a(n) = A067417(n+6, 6). %F A067422 a(n) = 9*(3*7)^(n-1), n >= 1, a(0)=1. %F A067422 G.f.: (1-12*x)/(1-21*x). %o A067422 (Magma) [Ceiling(9*(3*7)^(n-1)): n in [0..20]]; // _Vincenzo Librandi_, Oct 02 2011 %Y A067422 Cf. A067421 (sixth column), A067423 (eighth column), A009965 (powers of 21). %K A067422 nonn,easy %O A067422 0,2 %A A067422 _Wolfdieter Lang_, Jan 25 2002