cp's OEIS Frontend

A304371 Number of function calls of the second kind required to compute ack(3,n), where ack denotes the Ackermann function.

%I A304371 #13 Oct 22 2019 09:31:48
%S A304371 5,47,257,1187,5093,21095,85865,346475,1391981,5580143,22345073,
%T A304371 89429363,357815669,1431459191,5726229881,22905705851,91624396157,
%U A304371 366500730239,1466009212289,5864049431939,23456222893445,93824941905287,375299868284297,1501199674463627
%N A304371 Number of function calls of the second kind required to compute ack(3,n), where ack denotes the Ackermann function.
%C A304371 The distinction between different kinds of recursive calls is based on a naive implementation of the Ackermann function in C.
%C A304371 int ack(int m, int n)
%C A304371 {
%C A304371 // Final result
%C A304371 ....if (m==0) return n + 1;
%C A304371 .
%C A304371 // Recursive calls of the first kind:
%C A304371 ....if (n==0) return ack(m - 1, 1);
%C A304371 .
%C A304371 // Recursive calls of the second kind:
%C A304371 ....return ack(m - 1, ack(m, n - 1));
%C A304371 }
%H A304371 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (8,-21,22,-8).
%F A304371 A304370(n) + a(n) + 1 = A074877(n).
%F A304371 G.f.: (8*x^3-14*x^2+7*x+5)/((4*x-1)*(2*x-1)*(x-1)^2). - _Alois P. Heinz_, May 12 2018
%t A304371 LinearRecurrence[{8,-21,22,-8},{5,47,257,1187},30] (* _Harvey P. Dale_, Oct 22 2019 *)
%Y A304371 Cf. A036563, A074877, A304370.
%K A304371 nonn,easy
%O A304371 0,1
%A A304371 _Olivier Gérard_, May 11 2018