A069225 Numbers k such that phi(k) is the reversal of sigma(k).

1, 65, 2771, 10920, 158804, 2413091, 16636354, 117650080, 140766297, 630947067, 4639526938, 153896850898

Offset: 1

Author

Joseph L. Pe, Apr 12 2002

Keywords

• base
• nonn

Comments

a(13) > 10^12. - Giovanni Resta, Nov 03 2012

Examples

			phi(65) = 48 = reversal(84) = reversal(sigma(65)), so 65 belongs to the sequence.
n=2413091, sigma[n]=2528032, phi[n]=2308152=rev[sigma[n]].
		

Crossrefs

Cf. A000010, A000203, A004086.

Programs

Mathematica

Select[Range[10^6], EulerPhi[ # ] == FromDigits[Reverse[IntegerDigits[DivisorSigma[1, # ]]]] &]

Extensions

a(6)-a(8) from Labos Elemer, Oct 22 2004

a(9)-a(11) from Donovan Johnson, Jan 14 2011

a(12) from Giovanni Resta, Nov 03 2012