OFFSET
1,2
COMMENTS
a(n) = the smallest n-digit number of the form p^8 or p^2*q^2 (p, q = distinct primes), a(n) = 0 if no such number exists.
FORMULA
A000005(a(n)) = 9.
MATHEMATICA
Table[k=10^(n-1); While[k<10^n && DivisorSigma[0, k] != 9, k++]; If[k==10^n, k=0]; k, {n, 20}]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 27 2010
EXTENSIONS
Extended by T. D. Noe, Nov 29 2010
a(11)-a(25) from Robert Gerbicz, Nov 29 2010
STATUS
approved