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 A011921 #15 Jul 08 2025 02:42:31
%S A011921 0,0,0,0,2,10,32,76,152,274,458,720,1080,1560,2184,2978,3970,5192,
%T A011921 6676,8456,10570,13058,15960,19320,23184,27600,32618,38290,44672,
%U A011921 51820,59792,68650,78458,89280,101184
%N A011921 [ n(n-1)(n-2)(n-3)/11 ].
%H A011921 <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (4, -6, 4, -1, 0, 0, 0, 0, 0, 0, 1, -4, 6, -4, 1).
%F A011921 a(n) = +4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4) +a(n-11) -4*a(n-12) +6*a(n-13) -4*a(n-14) +a(n-15). G.f.: 2*x^4*(1+x+2*x^2+x^4+2*x^5+x^6+2*x^8+x^9+x^10) / ( (1-x)^5*(1+x+x^2+x^3+x^4+x^5+x^6+x^7+x^8+x^9+x^10) ). - _R. J. Mathar_, Apr 15 2010
%t A011921 Table[Floor[(n(n-1)(n-2)(n-3))/11],{n,0,40}] (* or *) LinearRecurrence[ {4,-6,4,-1,0,0,0,0,0,0,1,-4,6,-4,1},{0,0,0,0,2,10,32,76,152,274,458,720,1080,1560,2184},40] (* _Harvey P. Dale_, Oct 17 2012 *)
%o A011921 (PARI) a(n)=n*(n-1)*(n-2)*(n-3)\11 \\ _Charles R Greathouse IV_, Oct 18 2022
%K A011921 nonn,easy
%O A011921 0,5
%A A011921 _N. J. A. Sloane_