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A120161
a(n) = 2 + floor((1 + Sum_{j=1..n-1} a(j))/4).
1
2, 2, 3, 4, 5, 6, 7, 9, 11, 14, 18, 22, 28, 35, 43, 54, 68, 85, 106, 132, 165, 207, 258, 323, 404, 505, 631, 789, 986, 1232, 1540, 1925, 2407, 3008, 3760, 4700, 5875, 7344, 9180, 11475, 14344, 17930, 22412, 28015, 35019, 43774, 54717, 68397, 85496, 106870
OFFSET
1,1
LINKS
MATHEMATICA
f[s_]:= Append[s, Floor[(9 +Plus @@ s)/4]]; Nest[f, {2}, 49] (* Robert G. Wilson v, Jul 08 2006 *)
PROG
(Magma)
function f(n, a, b)
t:=0;
for k in [1..n-1] do
t+:= a+Floor((b+t)/4);
end for;
return t;
end function;
g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
A120161:= func< n | g(n, 2, 1) >;
[A120161(n): n in [1..60]]; // G. C. Greubel, Sep 02 2023
(SageMath)
@CachedFunction
def f(n, p, q): return p + (q + sum(f(k, p, q) for k in range(1, n)))//4
def A120161(n): return f(n, 2, 1)
[A120161(n) for n in range(1, 61)] # G. C. Greubel, Sep 02 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Graeme McRae, Jun 10 2006
EXTENSIONS
More terms from Robert G. Wilson v, Jul 08 2006
Name edited by G. C. Greubel, Sep 02 2023
STATUS
approved