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A276702
Numbers n>0 such that n’ = (n+1)’ + (n+2)’, where n’ is the arithmetic derivative of n.
0
28, 2056, 2865, 7157404, 10181420, 39593464, 92261602845
OFFSET
1,1
COMMENTS
a(8) > 5*10^12. - Giovanni Resta, Sep 16 2016
EXAMPLE
28’ = 32, 29’ = 1, 30’ = 31 and 32 = 1 + 31.
MAPLE
with(numtheory): P:= proc(q) local a, b, c, n, p;
a:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]);
b:=(n-1)*add(op(2, p)/op(1, p), p=ifactors(n-1)[2]);
c:=(n-2)*add(op(2, p)/op(1, p), p=ifactors(n-2)[2]);
if c=b+a then print(n-2); fi; od; end: P(10^9);
CROSSREFS
Cf. A003415.
Sequence in context: A294192 A202811 A285749 * A007219 A203751 A178187
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, Sep 15 2016
EXTENSIONS
a(7) from Giovanni Resta, Sep 16 2016
STATUS
approved