OFFSET
1,6
COMMENTS
For a given n this is a minimal solution of the Diophantine equation n^2 - k^2 = x^3 in positive integers. The solution exists only for n from A070745.
EXAMPLE
n = 3: 9 - k^2 = x^3 is true for k = 1 and x = 2, thus a(3) = 1.
n = 6: 36 - k^2 = x^3 is true for k = 3 and x = 3, thus a(6) = 3.
PROG
(Python)
from sympy import integer_nthroot
def A372644(n): return next((k for k in range(1, n) if integer_nthroot(n**2-k**2, 3)[1]), -1) # Chai Wah Wu, May 11 2024
CROSSREFS
KEYWORD
sign
AUTHOR
Ctibor O. Zizka, May 08 2024
STATUS
approved