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 A095152 #29 Mar 18 2024 16:46:56
%S A095152 1,32,321,2560,18881,135072,954241,6705920,47020161,329377312,
%T A095152 2306349761,16146574080,113032395841,791245902752,5538778714881,
%U A095152 38771623191040,271401878897921,1899814701967392,13298707562817601,93090966886860800,651636810049438401
%N A095152 Number of 3-block covers of a labeled n-set.
%H A095152 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (11,-31,21).
%F A095152 a(n) = (1/3!)*(11-6*3^n+7^n).
%F A095152 a(n) = 11*a(n-1)-31*a(n-2)+21*a(n-3). G.f.: -x^2*(21*x+1) / ((x-1)*(3*x-1)*(7*x-1)). - _Colin Barker_, Jul 12 2013
%F A095152 a(n) = sum(i=0..n, (-1)^i * C(n,i) * C(2^(n-i)-1,3) ). - _Geoffrey Critzer_, Aug 24 2014
%p A095152 seq((11-6*3^n+7^n)/6, n=2..50); # _Robert Israel_, Aug 25 2014
%t A095152 nn = 19; Table[Sum[(-1)^i Binomial[n, i] Binomial[2^(n - i) - 1, 3], {i, 0, n}], {n, 2, nn}] (* _Geoffrey Critzer_, Aug 24 2014 *)
%t A095152 Table[(11 - 6*3^n + 7^n)/6, {n, 2, 20}] (* _Wesley Ivan Hurt_, Aug 26 2014 *)
%o A095152 (Magma) [(11-6*3^n+7^n)/6 : n in [2..30]]; // _Wesley Ivan Hurt_, Aug 26 2014
%Y A095152 Column of A055154.
%K A095152 easy,nonn
%O A095152 2,2
%A A095152 _Vladeta Jovovic_, May 31 2004
%E A095152 More terms from _Colin Barker_, Jul 12 2013