A189558 Least number k>0 such that x' = k has n solutions, where x' is the arithmetic derivative (A003415) of x.

2, 4, 10, 16, 24, 54, 48, 60, 84, 90, 114, 144, 150, 120, 168, 234, 216, 252, 288, 210, 354, 240, 432, 360, 330, 552, 456, 390, 462, 480, 546, 420, 510, 600, 672, 792, 756, 714, 798, 690, 720, 630, 1116, 1026, 930, 780, 870, 960, 900, 924, 1134, 1296, 840

Offset: 0

Author

T. D. Noe, Apr 24 2011

Keywords

• nonn

Comments

It appears that all terms are even. See A189559 for k restricted to prime numbers and A189560 restricted to odd numbers.

References

• See A003415.

Links

• T. D. Noe and Donovan Johnson, Table of n, a(n) for n = 0..5000 (terms up to a(665) from T. D. Noe)

Crossrefs

See A003415, A099302, A189559, A189560.

Formula

a(n) is the least k>0 such that A099302(k) = n.