A259851 Numbers x such that x = concat(a, b) and a’ * b’ = x, where a’ and b’ are the arithmetic derivatives of a and b.

48, 448, 708, 6560, 279207, 350400, 1050000, 1837500, 2480128, 2600000, 4687500, 7562500, 10762500, 25712000, 27337500, 28650000, 34912500, 57450000, 62568960, 65312500, 65871440, 106505392, 153456128, 213939328, 245600000, 258332000, 281600000, 285650000

Offset

1,1

Links

Lars Blomberg, Table of n, a(n) for n = 1..58

Michel Marcus, x = a' * b'

OEIS Wiki, Arithmetic derivative.

Example

Consider 48 as concat(4,8). We have 4’ = 4, 8’ = 12 and 4 * 12 = 48.
Consider 448 as concat(4,48). We have 4’ = 4, 48’ = 112 and 4 * 112 = 448.

Maple

isA259851 := proc(x)
    local i, a, b;
    for i from 1 to ilog10(n) do
        a:=floor(n/10^i);
        b:=n-a*10^i;
        if A003415(a)*A003415(b) = x then
            return true;
        end  if;
    end do:
    false ;
end proc:
for n from 1 do
    if isA259851(n) then
        print(n) ;
    end if;
end do: # R. J. Mathar, Jul 08 2015

Crossrefs

Cf. A003415.

Sequence in context: A190416 A231342 A192828 * A223419 A333671 A287762

Adjacent sequences: A259848 A259849 A259850 * A259852 A259853 A259854

Keyword

nonn,base

Author

Paolo P. Lava, Jul 07 2015

Extensions

More terms from Lars Blomberg, Oct 03 2015

Status

approved