login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A120157
a(n) = 13 + floor(Sum_{j=1..n-1} a(j)/3).
1
13, 17, 23, 30, 40, 54, 72, 96, 128, 170, 227, 303, 404, 538, 718, 957, 1276, 1701, 2268, 3024, 4032, 5376, 7168, 9558, 12744, 16992, 22656, 30208, 40277, 53703, 71604, 95472, 127296, 169728, 226304, 301738, 402318, 536424, 715232, 953642
OFFSET
1,1
LINKS
MATHEMATICA
Module[{lst={13}}, Do[AppendTo[lst, 13+Floor[Total[lst]/3]], {40}]; lst] (* Harvey P. Dale, May 22 2012 *)
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) >;
A120157:= func< n | g(n, 13, 0) >;
[A120157(n): n in [1..60]]; // G. C. Greubel, Aug 31 2023
(SageMath)
@CachedFunction
def A120157(n): return 13 +(sum(A120157(k) for k in range(1, n)))//3
[A120157(n) for n in range(1, 61)] # G. C. Greubel, Aug 31 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Graeme McRae, Jun 10 2006
EXTENSIONS
Name edited by G. C. Greubel, Aug 31 2023
STATUS
approved