A276702 Numbers n>0 such that n’ = (n+1)’ + (n+2)’, where n’ is the arithmetic derivative of n.

28, 2056, 2865, 7157404, 10181420, 39593464, 92261602845

Offset

1,1

Comments

a(8) > 5*10^12. - Giovanni Resta, Sep 16 2016

Links

Table of n, a(n) for n=1..7.

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

Adjacent sequences: A276699 A276700 A276701 * A276703 A276704 A276705

Keyword

nonn,more

Author

Paolo P. Lava, Sep 15 2016

Extensions

a(7) from Giovanni Resta, Sep 16 2016

Status

approved