A293478 - OEIS

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A293478

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

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

(list; graph; refs; listen; history; text; internal format)

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);