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 A086790 #21 Jun 02 2025 00:16:14
%S A086790 1,2,4,8,11,15,19,23,26,30,34,38,42,46,50,54,58,62,66,70,74,78,82,86,
%T A086790 90,94,98,102,106,110,114,118,122,126,130,134,138,142,146,150,154,158,
%U A086790 162,166,170,174,178,182,186,190,194,198,202,206,210,214,218,222,226,230
%N A086790 a(n) = floor((1+n+2*n^2+4*n^3)/(1+2*n+n^2)).
%H A086790 Harvey P. Dale, <a href="/A086790/b086790.txt">Table of n, a(n) for n = 1..1000</a>
%H A086790 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F A086790 a(n) = floor(4*n-6+9/(n+1)-2/(n+1)^2). For n>=8 a(n)=4*n-6 - _Benoit Cloitre_, Aug 06 2003
%e A086790 a(2)=floor((1+2^1+2*2^2+4*2^3)/(1+2*2^1+2^2))=floor(43/9)=floor(4.77778)=4
%t A086790 LinearRecurrence[{2,-1},{1,2,4,8,11,15,19,23,26,30},60] (* _Harvey P. Dale_, Jun 20 2020 *)
%o A086790 (PARI) a(n)=floor(4*n-6+9/(n+1)-2/(n+1)^2) \\ _Charles R Greathouse IV_, Oct 07 2015
%K A086790 easy,nonn
%O A086790 1,2
%A A086790 Wang Dan (wangdan01(AT)lycos.com), Aug 04 2003
%E A086790 More terms from _Benoit Cloitre_, Aug 06 2003