A230006 Numbers k such that sigma(k) + phi(k) = reversal(k) + 1.

1, 37, 225, 397, 11112722, 1309286244182

Offset: 1

Author

Farideh Firoozbakht, Dec 02 2013

Keywords

• nonn
• base
• more

Comments

If p = 4*10^m-3 is prime then p is in the sequence.

a(7) > 10^13. - Giovanni Resta, Feb 08 2014

Examples

			sigma(37)+phi(37) = 38+36 = 73+1 = reversal(37)+1.
		

Crossrefs

Cf. A000010, A000203, A004086, A101398, A230004, A230005.

Programs

Mathematica

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

Extensions

a(6) from Giovanni Resta, Feb 06 2014