

A293478


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


0



17251, 109999, 112639, 130733, 269119, 318293, 390319, 463669, 1319519, 1726541, 1841839, 2010719, 2013187, 2311919, 5780221, 6493519, 7355839, 7533599, 10668773, 12652639, 14650639, 14951999, 21098459, 21500071, 25167845, 31008319, 35807999, 38687599, 39458719
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..29.


EXAMPLE

17251' = 1725' = 1340, so 17251 is a term.
109999' = 10999' = 664, so 109999 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:=trunc(n/10); 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. A010879 (LSD), A003415 (arithmetic derivative).
Sequence in context: A251207 A233993 A043621 * A076774 A236447 A094413
Adjacent sequences: A293475 A293476 A293477 * A293479 A293480 A293481


KEYWORD

nonn,base,easy


AUTHOR

Paolo P. Lava, Oct 10 2017


STATUS

approved



