A336898 - OEIS

%I #9 Aug 28 2020 10:16:18

%S 1,1,1,3,1,5,1,7,1,9,5,11,1,13,7,15,1,17,1,19,1,3,11,23,1,25,13,27,7,

%T 29,5,31,1,33,17,35,1,37,19,39,1,41,1,43,11,45,23,47,1,49,25,51,13,53,

%U 1,55,7,57,29,59,1,61,31,9,1,65,11,67,17,69,35,71,1,73

%N a(n) = numerator(n / (4^n - 2^n)) for n > 0 and a(0) = 1.

%e r(n) = 1, 1/2, 1/6, 3/56, 1/60, 5/992, 1/672, 7/16256, 1/8160, 9/261632, ...

%p r := n -> `if`(n=0, 1, n/(4^n - 2^n)): seq(numer(r(n)), n=0..72);

%o (PARI) a(n) = if (n==0, 1, numerator(n / (4^n - 2^n))); \\ _Michel Marcus_, Aug 28 2020

%Y Cf. A336899 (denominator).

%K nonn,frac

%O 0,4

%A _Peter Luschny_, Aug 28 2020