OFFSET
0,1
REFERENCES
Donald D. Spencer, Computers in Number Theory, Computer Science Press, Rockville MD, 1982, pp. 130-131.
FORMULA
The solutions are given by x = r^2+2*r*k+2*k^2, y = 2*k*(k+r) with r >= 1, k >= 1, r odd, gcd(r, k) = 1.
EXAMPLE
Pairs are [5, 4], [17, 8], [13, 12], [37, 12], [65, 16], [29, 20], [101, 20], ... E.g., 5-4=1^2, 5+4=3^2.
a(41) = 1765 because A120427(41) = 84 and we have gcd(1765,84)=1 and 1765-84 = 41^2 and 1765+84 = 43^2. - Sean A. Irvine, Jan 01 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 02 2001
EXTENSIONS
a(41) onward corrected by Sean A. Irvine, Jan 01 2023
STATUS
approved