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A105075
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a(1) = 1; a(n) = Sum_{k=1..n-1} phi(a(k)*a(n-k)), where phi(m) is the totient function.
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0
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1, 1, 2, 3, 6, 10, 16, 38, 80, 160, 328, 752, 1712, 4000, 8736, 16940, 34816, 83904, 178304, 433408, 1031552, 2601600, 5193984, 11318272, 26631680, 62674688, 160582656, 336680960, 715578368, 1829193728, 4724027392, 11004676992
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OFFSET
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1,3
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LINKS
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MAPLE
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with(numtheory): a:=array(1..100): a[1]:=1: for n from 1 to 49 do a[n+1]:=sum(phi(a[k]*a[n+1-k]), k=1..n) od: for i from 1 to 50 do printf(`%d, `, a[i]) od: # James A. Sellers, Apr 09 2005
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MATHEMATICA
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a[1] = 1; a[n_] := Sum[ EulerPhi[ a[k] a[n - k]], {k, n - 1}]; Table[ a[n], {n, 32}] (* Robert G. Wilson v, Apr 09 2005 *)
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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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