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 A060722 #31 Jul 02 2025 16:02:01
%S A060722 1,3,81,19683,43046721,847288609443,150094635296999121,
%T A060722 239299329230617529590083,3433683820292512484657849089281,
%U A060722 443426488243037769948249630619149892803
%N A060722 a(n) = 3^(n^2).
%C A060722 The number of n X n {-1,0,1}-matrices (the same as the number of n X n matrices over GF(3) ).
%H A060722 Harry J. Smith, <a href="/A060722/b060722.txt">Table of n, a(n) for n = 0..45</a>
%H A060722 Robert Corless and Steven Thornton, <a href="http://www.bohemianmatrices.com/assets/images/posters/The_Bohemian_Eigenvalue_Project-FIRS_2017.pdf">The Bohemian Eigenvalue Project</a>, 2017 poster.
%H A060722 Joël Gay and Vincent Pilaud, <a href="https://arxiv.org/abs/1804.06572">The weak order on Weyl posets</a>, arXiv:1804.06572 [math.CO], 2018.
%F A060722 a(n) = [x^n] 1/(1 - 3^n*x). - _Ilya Gutkovskiy_, Oct 10 2017
%F A060722 From _Geoffrey Critzer_, Dec 02 2024: (Start)
%F A060722 a(n) = Sum_{k=0..n} A378666(n,k)*A053764(k)*A053290(n-k).
%F A060722 Sum_{n>=0} a(n)x^n/B(n) = f(x)*g(x) where f(x) = Sum_{n>=0} A053290(n)x^n/B(n) and g(x) = Sum_{n>=0} A053764(n)x^n/B(n) and B(n) = A053290(n)/2^n. (End)
%p A060722 for n from 1 to 15 do printf(`%d,`,3^(n^2)) od:
%t A060722 Array[3^(#^2) &, 9] (* _Michael De Vlieger_, Jul 12 2018 *)
%o A060722 (PARI) { for (n=0, 45, write("b060722.txt", n, " ", 3^(n^2)); ) } \\ _Harry J. Smith_, Jul 10 2009
%o A060722 (PARI) a(n) = 3^(n^2); \\ _Joerg Arndt_, Feb 23 2014
%Y A060722 Cf. A053290, A053764, A378666.
%K A060722 nonn,easy
%O A060722 0,2
%A A060722 Avi Peretz (njk(AT)netvision.net.il), Apr 21 2001
%E A060722 More terms from _James Sellers_, Apr 24 2001
%E A060722 a(0) = 1 added by _N. J. A. Sloane_, Nov 23 2007