A237798 Numbers k such that phi(k) equals the product of two numbers: sums of prime factors of k, with and without repetition.

750, 5022, 8037, 18250, 60249, 105669, 1760490, 1965270, 4626489, 62546070, 202631245, 441416073, 286952692809

Offset

1,1

Comments

25446095286407049 and 27093686218810118911929 are terms.

Links

Table of n, a(n) for n=1..13.

Example

750 = 2*3*5^3 is a term since phi(750) = 200 = (2+3+5) * (2+3+5+5+5).

Mathematica

Select[Range[2, 10^5], (f=FactorInteger@#; EulerPhi[#] == Total[First /@ f]* Total[Times @@@ f]) &]

Crossrefs

Cf. A000010, A001414, A008472, A073396.

Sequence in context: A252533 A031968 A053331 * A015067 A129036 A290272

Adjacent sequences: A237795 A237796 A237797 * A237799 A237800 A237801

Keyword

nonn

Author

Giovanni Resta, Feb 13 2014

Status

approved