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A120169
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a(n) = 12 + floor((1 + Sum_{j=1..n-1} a(j))/4).
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5
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12, 15, 19, 23, 29, 36, 45, 57, 71, 89, 111, 139, 173, 217, 271, 339, 423, 529, 661, 827, 1033, 1292, 1615, 2018, 2523, 3154, 3942, 4928, 6160, 7700, 9625, 12031, 15039, 18798, 23498, 29372, 36715, 45894, 57368, 71710
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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[(t+49)/4]}, {t+c, c}]; NestList[nxt, {12, 12}, 40][[All, 2]] (* Harvey P. Dale, Jun 21 2017 *)
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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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