OFFSET
1,1
LINKS
EXAMPLE
a(1) = 4 because there are four primitive solutions (a, b, c, d) as follows: (1, 2, 2, 3), (2, 3, 6, 7), (1, 4, 8, 9), (4, 4, 7, 9) with d < 10.
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Arkadiusz Wesolowski, May 01 2013
EXTENSIONS
a(4) from Giovanni Resta, May 01 2013
a(5)-a(9) from Max Alekseyev, Feb 28 2023
STATUS
approved