A293477 Composite numbers k = concat(MSD(k),x) such that k' = x', where k' is the arithmetic derivative of k.

169, 1219, 1339, 1966, 3959, 7519, 11569, 17845, 35579, 37391, 38579, 77593, 94249, 94319, 95299, 96139, 97271, 97969, 99691, 106159, 107629, 115069, 137533, 150071, 168505, 188297, 247589, 339629, 345911, 352829, 362771, 363191, 365399, 370259, 381779, 382043

Offset

1,1

Links

Paolo P. Lava, Table of n, a(n) for n = 1..150

Example

169' = 69' = 26, so 169 is a term.
3959' = 959' = 144, so 3959 is a term.

Maple

with(numtheory): P:=proc(q) local a, k, n, p, x, y; for n from 2 to q do
if not isprime(n) then x:=n mod 10^(ilog10(n)); a:=x*add(op(2, p)/op(1, p), p=ifactors(x)[2]);
if n*add(op(2, p)/op(1, p), p=ifactors(n)[2])=a then print(n); fi; fi; od; end: P(10^6);

Crossrefs

Cf. A000030 (MSD), A003415 (arithmetic derivative).

Sequence in context: A250988 A289338 A256979 * A264304 A241538 A231974

Adjacent sequences: A293474 A293475 A293476 * A293478 A293479 A293480

Keyword

nonn,base,easy

Author

Paolo P. Lava, Oct 10 2017

Status

approved