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A120154
a(n) = 9 + floor( Sum_{j=1..n-1} a(j)/3 ).
1
9, 12, 16, 21, 28, 37, 50, 66, 88, 118, 157, 209, 279, 372, 496, 661, 882, 1176, 1568, 2090, 2787, 3716, 4955, 6606, 8808, 11744, 15659, 20879, 27838, 37118, 49490, 65987, 87983, 117310, 156414, 208552, 278069, 370759, 494345, 659127
OFFSET
1,1
LINKS
MATHEMATICA
A120154[n_]:= A120154[n]= 9 +Quotient[Sum[A120154[k], {k, n-1}], 3];
Table[A120154[n], {n, 60}] (* G. C. Greubel, Jun 20 2023 *)
PROG
(Magma)
function f(n, a, b)
t:=0;
for k in [1..n-1] do
t+:= a+Floor((b+t)/3);
end for;
return t;
end function;
g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
A120154:= func< n | g(n, 9, 0) >;
[A120154(n): n in [1..60]]; // G. C. Greubel, Jun 20 2023
(SageMath)
@CachedFunction
def A120154(n): return 9 + (sum(A120154(k) for k in range(1, n)))//3
[A120154(n) for n in range(1, 61)] # G. C. Greubel, Jun 20 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Graeme McRae, Jun 10 2006
STATUS
approved