Here powerful numbers are those for which every prime factor appears to a power at least 2.
Stephens, A. J. and Williams, H. C., Some computational results on a problem concerning powerful numbers, Math. Comp. 50 (1988), 619-632.
Table of n, a(n) for n=1..8.
Sequence in context: A077734 A272184 A213286 * A160285 A111304 A055751
Adjacent sequences: A135732 A135733 A135734 * A135736 A135737 A135738
N. J. A. Sloane, Mar 05 2008