OFFSET
1,2
COMMENTS
a(n) = the largest n-digit number of the form p^9 or p^4*q (p, q distinct primes), a(n) = 0 if no such number exists.
MATHEMATICA
Table[k=10^n-1; While[k>10^(n-1) && DivisorSigma[0, k] != 10, k--]; If[k==10^(n-1), k=0]; k, {n, 20}]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 27 2010
EXTENSIONS
Extended by T. D. Noe, Nov 29 2010
STATUS
approved