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A189941
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Numbers n such that n''' = n''+ 1 where n'' and n''' are respectively the second and the third arithmetic derivative of n.
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2
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186, 258, 322, 338, 3866, 4326, 4775, 18830, 19122, 27586, 34330, 34538, 41626, 46762, 49858, 49922, 54298, 55810, 70510, 82122, 86938, 89102, 101042, 101706, 106442, 110510, 112910, 118586, 120822, 129722, 133430, 134714, 150742, 157362, 158235, 163410
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OFFSET
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1,1
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COMMENTS
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The second arithmetic derivative of a(n) is a Giuga's number A007850 (solution of n'=n+1).
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LINKS
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EXAMPLE
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186'= 161; 186"=161' = 30; 186"'=30'= 31-> 186'''= 186" +1 -> a(1)=186.
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MAPLE
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Using Porter's code from A003415 der:=n->n*add(op(2, p)/op(1, p), p=ifactors(n)[2])
for i from 1 to n do a:=der(der(der(i)))-der(der(i))-1: if a=0 then j:=j+1; A[j]:=i: end if od
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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