OFFSET
1,1
COMMENTS
265247 is the first term that is prime; sigma(265247^3) = 18661780598460480 = 48432^3 + 264708^3. In other words, the equation (1 + p)*(1 + p^2) = a^3 + b^3 where p is prime and a, b > 0, is soluble.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..700
EXAMPLE
21 is a term because sigma(21^3) = 16000 = 20^3 + 20^3.
PROG
(PARI) isA003325(n) = for(k=1, sqrtnint(n\2, 3), ispower(n-k^3, 3) && return(1));
lista(nn) = for(n=1, nn, if(isA003325(sigma(n^3)), print1(n, ", ")));
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, May 01 2016
STATUS
approved