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 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. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified February 3 23:01 EST 2023. Contains 360045 sequences. (Running on oeis4.)