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 A026809 #19 Feb 28 2024 11:32:37 %S A026809 0,1,84,2925,85320,2362041,64304604,1741001445,47050068240, %T A026809 1270739210481,34313445309924,926494403955165,25015631334908760, %U A026809 675424587904113321,18236486750190760044,492385348146244352085,13294406252968671566880 %N A026809 a(n) = 3^n*(3^n-1)*(3^n-2)/6. %H A026809 G. C. Greubel, <a href="/A026809/b026809.txt">Table of n, a(n) for n = 0..690</a> %H A026809 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (39, -351, 729). %F A026809 a(n) = binomial(3^n, 3), n >= 0. - _Zerinvary Lajos_, Jan 07 2008 %p A026809 seq(binomial(3^n,3),n=0..16); # _Zerinvary Lajos_, Jan 07 2008 %t A026809 Binomial[3^Range[0, 20], 3] (* _G. C. Greubel_, Nov 08 2019 *) %o A026809 (PARI) vector(21, n, binomial(3^(n-1), 3) ) \\ _G. C. Greubel_, Nov 08 2019 %o A026809 (Magma) [Binomial(3^n, 3): n in [0..20]]; // _G. C. Greubel_, Nov 08 2019 %o A026809 (Sage) [binomial(3^n, 3) for n in (0..20)] # _G. C. Greubel_, Nov 08 2019 %o A026809 (GAP) List([0..20], n-> Binomial(3^n, 3) ); # _G. C. Greubel_, Nov 08 2019 %Y A026809 Subsequence of A000292. %K A026809 nonn %O A026809 0,3 %A A026809 _N. J. A. Sloane_