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%I #18 Oct 15 2015 17:28:25
%S 48,448,708,6560,279207,350400,1050000,1837500,2480128,2600000,
%T 4687500,7562500,10762500,25712000,27337500,28650000,34912500,
%U 57450000,62568960,65312500,65871440,106505392,153456128,213939328,245600000,258332000,281600000,285650000
%N Numbers x such that x = concat(a, b) and a’ * b’ = x, where a’ and b’ are the arithmetic derivatives of a and b.
%H Lars Blomberg, <a href="/A259851/b259851.txt">Table of n, a(n) for n = 1..58</a>
%H Michel Marcus, <a href="/A259851/a259851.txt">x = a' * b'</a>
%H OEIS Wiki, <a href="http://oeis.org/wiki/Arithmetic_derivative">Arithmetic derivative</a>.
%e Consider 48 as concat(4,8). We have 4’ = 4, 8’ = 12 and 4 * 12 = 48.
%e Consider 448 as concat(4,48). We have 4’ = 4, 48’ = 112 and 4 * 112 = 448.
%p isA259851 := proc(x)
%p local i,a,b;
%p for i from 1 to ilog10(n) do
%p a:=floor(n/10^i);
%p b:=n-a*10^i;
%p if A003415(a)*A003415(b) = x then
%p return true;
%p end if;
%p end do:
%p false ;
%p end proc:
%p for n from 1 do
%p if isA259851(n) then
%p print(n) ;
%p end if;
%p end do: # _R. J. Mathar_, Jul 08 2015
%Y Cf. A003415.
%K nonn,base
%O 1,1
%A _Paolo P. Lava_, Jul 07 2015
%E More terms from _Lars Blomberg_, Oct 03 2015
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