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 A259858 #14 Mar 08 2022 16:47:51 %S A259858 1,1,3,11,42,165,654,2605,10398,41550,166116,664299,2656866,10626810, %T A259858 42505932,170021123,680079282,2720306730,10881206124,43524782946, %U A259858 174099048684,696396028620,2785583782248,11142334464693,44569336530174,178277343463830,713109368541588 %N A259858 A bisection of A002083. %D A259858 H. Brocard, Query 4293, L'Intermédiaire des Mathématiciens, 23 (1916), 58-59. - _N. J. A. Sloane_, Mar 08 2022 %F A259858 a(0)=a(1)=1; a(2)=3; a(n) = 4*a(n-1) + ((-1)^(n-1)-3)/2 * a(floor((n-1)/2)). - _Carl R. White_, Oct 06 2017 %p A259858 A259858 := proc(n) %p A259858 A002083(2*n+1) ; %p A259858 end proc: %p A259858 seq(A259858(n),n=0..30) ; # _R. J. Mathar_, Jul 09 2015 %t A259858 a[n_] := a[n] = If[n < 3, 1 + 2 Boole@ PrimeQ@ n, 4 a[n - 1] + ((-1)^(n - 1) - 3)/2*a[Floor[(n - 1)/2]]]; Array[a, 27, 0] (* _Michael De Vlieger_, Oct 06 2017 *) %Y A259858 Cf. A002083, A245094. %K A259858 nonn %O A259858 0,3 %A A259858 _N. J. A. Sloane_, Jul 07 2015