A071525 Numbers n such that sigma(phi(n)) = reversal(n).

1, 3, 304, 918, 23922, 2388063, 88423222968, 655516144546

Offset: 1

Author

Joseph L. Pe, Jun 02 2002

Keywords

• base
• nonn

Comments

There are no other terms up to 10^7. - Jason Earls, Jun 04 2002

There are no other terms up to 45*10^7. - Farideh Firoozbakht, Dec 26 2007

There are no other terms up to 10^10. - Donovan Johnson, Oct 24 2013

a(9) > 10^12. - Giovanni Resta, Nov 10 2017

Examples

			sigma(phi(304)) = 403 = reverse(304).
		

Crossrefs

Cf. A000010, A000203, A135238.

Programs

Mathematica

Select[Range[10^5], DivisorSigma[1, EulerPhi[ # ]] == FromDigits[Reverse[IntegerDigits[ # ]]] &]

Extensions

More terms from Jason Earls, Jun 04 2002

Definition restored by Farideh Firoozbakht, Dec 26 2007

a(7)-a(8) from Giovanni Resta, Nov 10 2017