A209192 Numbers n such that digital root of n equals largest prime factor of n.

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

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

PrimeFan, Listing of Esoteric Integer Sequences

PrimeFan, Esoteric Integer Sequences [Cached copy]

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

Adjacent sequences: A209189 A209190 A209191 * A209193 A209194 A209195

Keyword

nonn,base,changed

Author

N. J. A. Sloane, Mar 05 2012

Status

approved