OFFSET
1,7
COMMENTS
Number of integers d from 0 to n-1 such that x^3 + y^3 == d (mod n) has no solutions in integers.
PROG
(Python) [n-len(set((pow(x, 3, n)+pow(y, 3, n))%n for x in range(n) for y in range(x+1))) for n in range(1, 51)]
(PARI) a(n) = my(v=[]); for (x=1, n, for (y=1, n, v = concat(v, Mod(x, n)^3 + Mod(y, n)^3))); n - #Set(v); \\ Michel Marcus, Jul 10 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Jack Zhang, May 27 2018
EXTENSIONS
a(50)-a(83) from Jon E. Schoenfield, May 28 2018
STATUS
approved