# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a106833 Showing 1-1 of 1 %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 Index entries for linear recurrences with constant coefficients, 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 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE