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A327442
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a(0) = 0; thereafter a(n) = a(n-1) + phi(n) if phi(n) > a(n-1), otherwise a(n) = a(n-1) - phi(n), where phi is the Euler phi-function A000010.
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6
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0, 1, 0, 2, 0, 4, 2, 8, 4, 10, 6, 16, 12, 0, 6, 14, 6, 22, 16, 34, 26, 14, 4, 26, 18, 38, 26, 8, 20, 48, 40, 10, 26, 6, 22, 46, 34, 70, 52, 28, 12, 52, 40, 82, 62, 38, 16, 62, 46, 4, 24, 56, 32, 84, 66, 26, 2, 38, 10, 68, 52, 112, 82, 46, 14, 62, 42, 108, 76, 32, 8, 78, 54, 126, 90
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graph;
refs;
listen;
history;
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internal format)
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OFFSET
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0,4
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LINKS
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N. J. A. Sloane, Table of n, a(n) for n = 0..9999
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MAPLE
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a:= proc(n) option remember; `if`(n<1, 0, ((s, t)-> s+
`if`(s<t, t, -t))(a(n-1), numtheory[phi](n)))
end:
seq(a(n), n=0..80); # Alois P. Heinz, Jan 11 2020
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MATHEMATICA
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a[0] = 0; a[n_] := a[n] = With[{phi = EulerPhi[n], a1 = a[n-1]}, If[phi>a1, a1+phi, a1-phi]];
a /@ Range[0, 80] (* Jean-François Alcover, Nov 01 2020 *)
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CROSSREFS
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Cf. A000010, A008344.
Sequence in context: A328598 A284010 A278082 * A068773 A234312 A244136
Adjacent sequences: A327439 A327440 A327441 * A327443 A327444 A327445
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Sep 12 2019
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STATUS
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approved
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