

A230019


Numbers n such that sigma(n) + phi(n) = reversal(n)  3.


4




OFFSET

1,1


COMMENTS

If n=2*10^m7 is a semiprime then n is in the sequence. Also if p=(1/999)*(962*1000^m+37) is prime then 18*p is in the sequence. All known terms are of these two forms.


LINKS



MATHEMATICA

r[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[If[DivisorSigma[1, n] + EulerPhi[n] == r[n]3, Print[n]], {n, 1000000000}]


CROSSREFS



KEYWORD

nonn,base,more


AUTHOR



EXTENSIONS



STATUS

approved



