%I #19 Sep 08 2022 08:45:57

%S 0,0,1,1,2,4,8,15,26,48,89,163,303,564,1057,1985,3744,7084,13443,

%T 25575,48770,93206,178481,342392,657930,1266204,2440322,4709393,

%U 9099506,17602324,34087042,66076419,128207978,248983611,483939977,941362695,1832519379

%N a(n) = floor((-1 + 2^n)/(1 + 2*n)).

%H Vincenzo Librandi, <a href="/A191630/b191630.txt">Table of n, a(n) for n = 1..1000</a>

%t f[n_] := Floor[(-1 + 2^n)/(2 n + 1)]

%t Table[f[n], {n, 1, 40}] (* A191630 *)

%o (Magma) [Floor((-1 + 2^n)/(2*n + 1)): n in [1..50]]; // _Vincenzo Librandi_, Sep 12 2011

%o (Maxima) A191630(n):=floor((-1+2^n)/(1+2*n))$ makelist(A191630(n),n,1,30); /* _Martin Ettl_, Oct 25 2012 */

%o (PARI) a(n) = (2^n-1)\(2*n+1); \\ _Altug Alkan_, Sep 08 2018

%Y Cf. A191633.

%K nonn

%O 1,5

%A _Clark Kimberling_, Jun 09 2011