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A120167
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a(n) = 9 + floor((3 + Sum_{j=1..n-1} a(j))/4).
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3
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9, 12, 15, 18, 23, 29, 36, 45, 56, 70, 88, 110, 137, 171, 214, 268, 335, 418, 523, 654, 817, 1021, 1277, 1596, 1995, 2494, 3117, 3896, 4870, 6088, 7610, 9512, 11890, 14863, 18579, 23223, 29029, 36286, 45358, 56697
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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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nxt[{t_, a_}]:=Module[{c=Floor[(39+t)/4]}, {t+c, c}]; NestList[nxt, {9, 9}, 40][[All, 2]] (* Harvey P. Dale, Apr 24 2019 *)
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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)/4);
end for;
return t;
end function;
g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
(SageMath)
@CachedFunction
def f(n, p, q): return p + (q +sum(f(k, p, q) for k in range(1, n)))//4
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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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STATUS
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approved
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