A287059 Least numbers k > 1 such that k'' = n*k', where k' and k'' are the first and the second arithmetic derivatives of k.

2, 4, 12, 160, 1255, 256, 12279, 3072, 1113823, 119120, 2191040, 4640768, 1835008, 12805120, 134217728

Offset

0,1

Links

Table of n, a(n) for n=0..14.

Example

a(3) = 160 because 160'' / 160' = 1296 / 432 = 3 and this is the least number to have this property.

Maple

with(numtheory): P:=proc(q) local a, b, k, n, p; for n from 0 to q do
for k from 2 to q do a:=k*add(op(2, p)/op(1, p), p=ifactors(k)[2]); b:=a*add(op(2, p)/op(1, p), p=ifactors(a)[2]); if b=n*a then print(k); break;
fi; od; od; end: P(10^9);

Crossrefs

Cf. A003415, A068346.

Sequence in context: A053040 A154734 A291827 * A059085 A030064 A224886

Adjacent sequences: A287056 A287057 A287058 * A287060 A287061 A287062

Keyword

nonn,more

Author

Paolo P. Lava, May 19 2017

Status

approved