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 A106833 #45 Sep 02 2024 04:28:17
%S A106833 3,4,9,8,15,12,21,16,27,20,33,24,39,28,45,32,51,36,57,40,63,44,69,48,
%T A106833 75,52,81,56,87,60,93,64,99,68,105,72,111,76,117,80,123,84,129,88,135,
%U A106833 92,141,96,147,100,153,104,159,108,165,112,171,116,177,120,183
%N A106833 3n and 2n, alternating.
%H A106833 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,0,-1).
%F A106833 a(n) = n*(2 + (n mod 2)).
%F A106833 a(2*n) = 6*n + 3 = A016945(n). - _Paul Curtz_, Nov 23 2008
%F A106833 a(2*n+1) = A008586(n+1).
%F A106833 From _R. J. Mathar_, Apr 08 2009: (Start)
%F A106833 G.f.: x*(3+4*x+3*x^2)/((x-1)^2*(1+x)^2).
%F A106833 a(n) = 2*a(n-2) - a(n-4). (End)
%F A106833 a(n) = Sum_{d|n} mu(d)*sigma(2*n/d). - _Benoit Cloitre_, Oct 18 2009
%F A106833 a(n) = n*(5-(-1)^n)/2. - _Wesley Ivan Hurt_, May 14 2014
%t A106833 Table[n(2 + Mod[n, 2]), {n, 50}]
%o A106833 (PARI) a(n)=sumdiv(n,d,moebius(d)*sigma(2*n/d)) \\ _Benoit Cloitre_, Oct 18 2009
%Y A106833 Cf. A118402 (first differences).
%K A106833 nonn,easy
%O A106833 1,1
%A A106833 _Zak Seidov_, May 19 2005
%E A106833 More terms from _Michel Marcus_, May 17 2014