A145745 Numbers n such that n = sigma(sum of digits of n)*sigma(product of digits of n).

1, 12, 6266169, 6931848

Offset

1,2

Comments

No further terms up to 10^26. - Chai Wah Wu, Nov 28 2015

No other terms below 10^100. The sequence is likely finite and complete. - Max Alekseyev, Sep 05 2023

Links

Table of n, a(n) for n=1..4.

Example

12 = 4*3 = sigma(1+2)*sigma(1*2).
6931848 = 56*123783 = sigma(6+9+3+1+8+4+8)*sigma(6*9*3*1*8*4*8).

Mathematica

Do[h=IntegerDigits[n]; s=Apply[Plus, h]; p=Apply[Times, h]; If[n== DivisorSigma[1, s]*DivisorSigma[1, p], Print[n]], {n, 2000000000}]

Crossrefs

Cf. A038369.

Sequence in context: A013862 A116233 A350543 * A175906 A144546 A165970

Adjacent sequences: A145742 A145743 A145744 * A145746 A145747 A145748

Keyword

base,more,nonn

Author

Farideh Firoozbakht, Oct 26 2008

Status

approved