OFFSET
1,1
COMMENTS
For any n, the equation x^3 + y^3 = a(n)*z^3 is not solvable in nonzero integers. Therefore, these numbers do not occur in A020898.
REFERENCES
Henri Cohen, Number Theory. Volume I: Tools and Diophantine Equations, Graduate Texts in Mathematics 239, Springer, 2007, pp. 374-375.
LINKS
Wikipedia, Prime power
PROG
(PARI) forstep(n=3, 839, 2, p=isprimepower(n); if(p>0, m=Mod(round(n^(1/p)), 9); if(m==2||m==5, print1(n, ", "))));
CROSSREFS
KEYWORD
nonn
AUTHOR
Arkadiusz Wesolowski, Aug 23 2013
STATUS
approved