A348283 Numbers k such that k' | k.

2, 3, 4, 5, 7, 11, 13, 17, 19, 23, 27, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293

Offset

1,1

Comments

Here, m' denotes the arithmetic derivative of m (A003415).

Not the same as A211781 since this sequence does not contain 225, 252, etc.

All prime numbers p are in the sequence since p' = 1 | p.

Links

Table of n, a(n) for n=1..64.

Example

127 is in the sequence since 127' = 1 | 127.

Maple

q:= n-> is(irem(n, n*add(i[2]/i[1], i=ifactors(n)[2]))=0):
select(q, [$2..300])[];  # Alois P. Heinz, Oct 11 2021

Prog

(PARI) ad(n) = vecsum([n/f[1]*f[2]|f<-factor(n+!n)~]); \\ A003415
isok(k) = (k>1) && !(k % ad(k)); \\ Michel Marcus, Oct 10 2021

Crossrefs

Cf. A003415, A211781.

Sequence in context: A284696 A033070 A211781 * A046022 A175787 A345899

Adjacent sequences: A348280 A348281 A348282 * A348284 A348285 A348286

Keyword

nonn

Author

Wesley Ivan Hurt, Oct 09 2021

Status

approved