OFFSET
0,5
COMMENTS
There are no such quadruples with diagonal 2n. - Michael Somos, Nov 17 2018
LINKS
Eric Weisstein's World of Mathematics, Pythagorean Quadruple.
MATHEMATICA
a[ n_] := With[ {w = 2 n + 1}, Sum[ Boole[x^2 + y^2 + z^2 == w^2 && 1 == GCD[x, y, z, w]], {z, w - 1}, {y, z}, {x, y}]]; (* Michael Somos, Nov 17 2018 *)
PROG
(PARI) {a(n) = my(w = 2*n+1); sum(z=1, w-1, sum(y=1, z, sum(x=1, y, x^2 + y^2 + z^2 == w^2 && 1 == gcd([x, y, z, w]))))}; /* Michael Somos, Nov 17 2018 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Ray Chandler, Aug 16 2004
STATUS
approved