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A120159
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a(n) = 15 + floor((2 + Sum_{j=1..n-1} a(j))/3).
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1
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15, 20, 27, 36, 48, 64, 85, 114, 152, 202, 270, 360, 480, 640, 853, 1137, 1516, 2022, 2696, 3594, 4792, 6390, 8520, 11360, 15146, 20195, 26927, 35902, 47870, 63826, 85102, 113469, 151292, 201723, 268964, 358618, 478158, 637544, 850058, 1133411
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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PROG
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(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) >;
(SageMath)
@CachedFunction
def A120159(n): return 15 +(2+sum(A120159(k) for k in range(1, n)))//3
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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