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 A055995 #18 Jun 13 2015 00:50:16
%S A055995 1,7,64,576,5184,46656,419904,3779136,34012224,306110016,2754990144,
%T A055995 24794911296,223154201664,2008387814976,18075490334784,
%U A055995 162679413013056,1464114717117504,13177032454057536,118593292086517824
%N A055995 a(n) = 64*9^(n-2), a(0)=1, a(1)=7.
%C A055995 For n>=2, a(n) is equal to the number of functions f:{1,2,...,n}->{1,2,3,4,5,6,7,8,9} such that for fixed, different x_1, x_2 in {1,2,...,n} and fixed y_1, y_2 in {1,2,3,4,5,6,7,8,9} we have f(x_1)<>y_1 and f(x_2)<> y_2. - _Milan Janjic_, Apr 19 2007
%C A055995 a(n) is the number of generalized compositions of n when there are 8*i-1 different types of i, (i=1,2,...). - _Milan Janjic_, Aug 26 2010
%D A055995 A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
%H A055995 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%H A055995 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (9)
%F A055995 a(n) = 9a(n-1) + ((-1)^n)*C(2, 2-n).
%F A055995 G.f.: (1-x)^2/(1-9x).
%F A055995 a(n) = Sum_{k, 0<=k<=n} A201780(n,k)*7^k. - _Philippe Deléham_, Dec 05 2011
%Y A055995 Second differences of 9^n (A001019). Cf. A055275.
%K A055995 easy,nonn
%O A055995 0,2
%A A055995 _Barry E. Williams_, Jun 04 2000