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A189941
Numbers n such that n''' = n''+ 1 where n'' and n''' are respectively the second and the third arithmetic derivative of n.
2
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
OFFSET
1,1
COMMENTS
The second arithmetic derivative of a(n) is a Giuga's number A007850 (solution of n'=n+1).
LINKS
EXAMPLE
186'= 161; 186"=161' = 30; 186"'=30'= 31-> 186'''= 186" +1 -> a(1)=186.
MAPLE
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
CROSSREFS
Sequence in context: A214605 A186398 A124207 * A362811 A363681 A260923
KEYWORD
nonn
AUTHOR
Giorgio Balzarotti, May 01 2011
STATUS
approved