OFFSET
1,2
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..365
EXAMPLE
n=43:sigma[43]=44; regular solutions:repdigit-1=prime.
MATHEMATICA
rd[x_] := Length[Union[IntegerDigits[x]]] Do[s = rd[DivisorSigma[1, n]]; s1 = DivisorSigma[1, n]; If[Equal[s, 1], Print[{n, s1}]; ta[[u]] = n; u = u + 1], {n, 1, 1000000}]; ta; DivisorSigma[1, ta]
Select[Range[650000], Length[Union[IntegerDigits[DivisorSigma[1, #]]]]==1&] (* Harvey P. Dale, May 11 2019 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Labos Elemer, Jul 15 2004
STATUS
approved