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 A011860 #13 Jul 08 2025 02:40:53 %S A011860 0,0,0,0,1,2,4,6,8,10,12,15,18,22,26,30,34,38,43,48,54,60,66,72,78,85, %T A011860 92,100,108,116,124,132,141,150,160,170,180,190,200,211,222,234,246, %U A011860 258,270,282,295,308,322,336,350,364,378,393,408,424,440,456,472,488,505 %N A011860 Floor( n(n-1)/7 ). %H A011860 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,0,0,0,1,-2,1). %F A011860 a(n) = +2*a(n-1) -a(n-2) +a(n-7) -2*a(n-8) +a(n-9). G.f.: x^4*(x^2+1)/ ((1-x)^3 * (1+x+x^2+x^3+x^4+x^5+x^6)). [_R. J. Mathar_, Apr 15 2010] %K A011860 nonn,easy %O A011860 0,6 %A A011860 _N. J. A. Sloane_