A178323 Numbers n such that phi(reversal(n)) + sigma(reversal(n)) = n.

572, 592, 5992, 599992, 2014080, 5999992, 594637872, 599999992, 599999999992

Offset: 1

Author

Farideh Firoozbakht, May 28 2010

Keywords

• nonn
• base
• more

Comments

If n is in the sequence A070272 then reversal(n) is in this sequence. 10 divides all other terms of the sequence. 2014080 is the only known such term.

If p=6*10^n-1 is a prime greater than 5 then reversal(5*p) is in the sequence, see comment lines of A070272.

There is no further term up to 10^9.

10^12 < a(10) <= 1442827967760. - Giovanni Resta, Sep 04 2018

Examples

			2014080 = phi(804102) + sigma(804102), so 2014080 is in the sequence.
		

Crossrefs

Cf. A000010, A000203, A004086, A070272, A178324, A178325.

Programs

Mathematica

r[n_]:=FromDigits[Reverse[IntegerDigits[n]]];
Do[If[EulerPhi[r[n]]+DivisorSigma[1,r[n]]==n,Print[n]],{n,1000000000}]

Extensions

a(9) from Giovanni Resta, Sep 04 2018