A233467 Numbers n such that sigma(n) = reversal(3n).

14, 134, 164, 1333334, 133333334, 929247534, 1333333334, 133333333334

Offset: 1

Author

Farideh Firoozbakht, Mar 14 2014

Keywords

• nonn
• base
• more

Comments

If m is a natural number and p=(2*10^m+1)/3 is prime then 2*p is in the sequence (see A096507).

a(9) > 10^12. - Giovanni Resta, Mar 15 2014

Examples

			sigma(14)=24=reversal(42)=reversal(3*14).
		

Crossrefs

Cf. A000203, A004086, A233465.

Programs

Mathematica

rev[n_] := FromDigits@ Reverse@ IntegerDigits@n; Select[Range[2*10^6], DivisorSigma[1, #] == rev[3*#] &] (* Giovanni Resta, Mar 15 2014 *)

Extensions

a(6)-a(8) from Giovanni Resta, Mar 15 2014