A056138 Number of ways in which n can be the shorter leg (shortest side) of an integer-sided right triangle.

0, 0, 1, 0, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 3, 2, 1, 2, 1, 3, 3, 1, 1, 4, 2, 1, 3, 3, 1, 3, 1, 3, 4, 1, 3, 5, 1, 1, 4, 5, 1, 3, 1, 3, 5, 1, 1, 7, 2, 2, 4, 3, 1, 3, 3, 5, 4, 1, 1, 9, 1, 1, 5, 4, 4, 4, 1, 3, 4, 3, 1

Offset: 1

Author

Henry Bottomley, Jun 15 2000

Keywords

• nonn

Crossrefs

Cf. A009004, A055525, A055527.

Programs

PARI

a(n)=my(b);sum(c=n+2,n^2\2+1,issquare(c^2-n^2,&b) && nCharles R Greathouse IV, Jul 07 2013

Formula

a(n) = A046079(n) - A056137(n) = A046081(n) - A046080(n) - A056137(n).