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A120170
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a(n) = ceiling( Sum_{i=1..n-1} a(i)/5 ), a(1)=1.
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10
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1, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 6, 7, 8, 10, 12, 14, 17, 21, 25, 30, 36, 43, 52, 62, 74, 89, 107, 128, 154, 185, 222, 266, 319, 383, 460, 552, 662, 795, 954, 1144, 1373, 1648, 1977, 2373, 2847, 3417, 4100, 4920, 5904, 7085, 8502, 10202, 12243, 14691, 17630
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listen;
history;
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internal format)
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OFFSET
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1,7
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LINKS
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MATHEMATICA
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f[s_] := Append[s, Ceiling[Plus @@ s/5]]; Nest[f, {1}, 57] (* Robert G. Wilson v, Jul 07 2006 *)
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PROG
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(SageMath)
@CachedFunction
def a(n):
if (n==1): return 1
else: return ceil(sum(a(k)/5 for k in (1..n-1)))
(Magma)
function f(n, a, b)
t:=0;
for k in [1..n-1] do
t+:= a+Ceiling ((b+t)/5);
end for;
return t;
end function;
g:= func< n, a, b | f(n+1, a, b)-f(n, a, b) >;
A120170:= func< n | n eq 1 select 1 else g(n-1, 1, -4) >;
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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