OFFSET
1,2
COMMENTS
Number of terms of this sequence up to 15000000 is 72. Has this sequence at least one multi-digit prime term?
EXAMPLE
97888745 is in the sequence because sigma(97888745) = 117936000 = sigma(9)*sigma(7)*sigma(8)*sigma(8)*sigma(8)*sigma(7)*sigma(4)*sigma(5).
MATHEMATICA
Do[If[h=IntegerDigits[n]; l=Length[h]; !MemberQ[h, 0]&&DivisorSigma[ 1, n]==Product[DivisorSigma[1, h[[k]]], {k, l}], Print[n]] {n, 100000000}]
Select[Range[24*10^5], DivisorSigma[1, #]==Times@@DivisorSigma[1, IntegerDigits[ #]]&] (* Harvey P. Dale, Mar 07 2018 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Farideh Firoozbakht, Oct 03 2004
STATUS
approved