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 A173123 #17 Aug 29 2022 04:41:40
%S A173123 1,60,1980,47520,926640,15567552,233513280,3202467840,40831464960,
%T A173123 489977579520,5585744406528,60935393525760,639821632020480,
%U A173123 6496650417438720,64038411257610240,614768748073058304,5763457013184921600,52888193768049868800,475993743912448819200
%N A173123 a(n) = binomial(n+9,9)*6^n.
%C A173123 With a different offset, number of n-permutations (n>=9) of 7 objects: r, s, t, u, v, z, x, y with repetition allowed, containing exactly 9 u's.
%H A173123 Vincenzo Librandi, <a href="/A173123/b173123.txt">Table of n, a(n) for n = 0..400</a>
%H A173123 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (60,-1620,25920,-272160,1959552,-9797760,33592320,-75582720,100776960,-60466176).
%F A173123 a(n) = C(n + 9, 9)*6^n.
%F A173123 From _Chai Wah Wu_, Nov 12 2021: (Start)
%F A173123 a(n) = 60*a(n-1) - 1620*a(n-2) + 25920*a(n-3) - 272160*a(n-4) + 1959552*a(n-5) - 9797760*a(n-6) + 33592320*a(n-7) - 75582720*a(n-8) + 100776960*a(n-9) - 60466176*a(n-10) for n > 9.
%F A173123 G.f.: 1/(6*x - 1)^10. (End)
%F A173123 From _Amiram Eldar_, Aug 29 2022: (Start)
%F A173123 Sum_{n>=0} 1/a(n) = 21093750*log(6/5) - 107683641/28.
%F A173123 Sum_{n>=0} (-1)^n/a(n) = 311299254*log(7/6) - 959739813/20. (End)
%t A173123 Table[Binomial[n + 9, 9]*6^n, {n, 0, 20}]
%o A173123 (Magma) [6^n* Binomial(n+9, 9): n in [0..20]]; // _Vincenzo Librandi_, Oct 12 2011
%Y A173123 Cf. A081136, A081144, A139626, A036084, A050988, A141407, A172501.
%K A173123 nonn,easy
%O A173123 0,2
%A A173123 _Zerinvary Lajos_, Feb 10 2010