OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Divisor Product
EXAMPLE
6 is in the sequence because 6 has 4 divisors {1,2,3,6} and 1*2*3*6 = 36;
25 is in the sequence because 25 has 3 divisors (1,5,25} and 1*5*25 = 125;
75 is in the sequence because 75 has 6 divisors {1,3,5,15,25,75} and 1*3*5*15*25*75 = 421875, etc.
MATHEMATICA
Select[Range[15000000], Mod[Sqrt[#1]^DivisorSigma[0, #1], 10^IntegerLength[#1]] == #1 && !PrimeQ[#1] & ]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Nov 23 2016
STATUS
approved