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A209192
Numbers n such that digital root of n equals largest prime factor of n.
1
2, 3, 5, 7, 12, 48, 50, 70, 128, 192, 196, 320, 448, 500, 700, 768, 1960, 2401, 3072, 3200, 4480, 5000, 5488, 7000, 8192, 8575, 12288, 12544, 19600, 20480, 24010, 28672, 30625, 32000, 44800, 49152, 50000, 54880, 67228, 70000, 78125, 85750, 109375, 125440
OFFSET
1,1
MAPLE
A010888 := proc(n)
d := (add(d, d=convert(n, base, 10))) mod 9 ;
if d = 0 then
return 9;
else
return d;
end if;
end proc:
isA209192 := proc(n)
A010888(n) = A006530(n) ;
end proc:
for n from 2 to 40000 do if isA209192(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Mar 22 2012
MATHEMATICA
drlpfQ[n_]:=NestWhile[Total[IntegerDigits[#]]&, n, #>9&]==FactorInteger[n][[-1, 1]]; Select[Range[2, 126000], drlpfQ] (* Harvey P. Dale, Sep 26 2024 *)
CROSSREFS
Sequence in context: A060528 A273728 A117593 * A052021 A217396 A126057
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Mar 05 2012
STATUS
approved