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 A036405 #18 Jul 20 2025 07:31:22
%S A036405 0,1,1,2,3,4,6,7,10,12,15,18,21,25,28,33,37,42,47,52,58,63,70,76,83,
%T A036405 90,97,105,112,121,129,138,147,156,166,175,186,196,207,218,229,241,
%U A036405 252,265,277,290,303,316,330,343,358,372,387,402,417,433,448
%N A036405 a(n) = ceiling(n^2/7).
%H A036405 <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 A036405 a(n) = +2*a(n-1) -a(n-2) +a(n-7) -2*a(n-8) +a(n-9). G.f.: x*(1+x)*(x^2-x+1)*(x^4-x^3+x^2-x+1) / ( (x^6+x^5+x^4+x^3+x^2+x+1)*(1-x)^3 ). [_R. J. Mathar_, Jul 06 2010]
%p A036405 A036405:=n->ceil(n^2/7): seq(A036405(n), n=0..100); # _Wesley Ivan Hurt_, Jan 16 2017
%t A036405 Ceiling[Range[0,60]^2/7] (* or *) LinearRecurrence[{2,-1,0,0,0,0,1,-2,1},{0,1,1,2,3,4,6,7,10},60] (* _Harvey P. Dale_, Jun 23 2015 *)
%K A036405 nonn,easy
%O A036405 0,4
%A A036405 _N. J. A. Sloane_