A070102 Number of obtuse integer triangles with perimeter n and relatively prime side lengths.

0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 2, 0, 2, 1, 3, 2, 3, 2, 5, 3, 6, 2, 8, 5, 9, 5, 9, 6, 11, 6, 14, 9, 14, 9, 17, 11, 19, 12, 19, 15, 23, 13, 27, 18, 26, 16, 32, 20, 33, 21, 34, 26, 40, 23, 42, 29, 42, 29, 50, 32, 53, 35, 48, 41, 58, 37, 64, 45, 60, 42, 71

Offset

1,11

Comments

a(n) = A051493(n) - A070094(n) - A070109(n).

Links

Table of n, a(n) for n=1..71.

R. Zumkeller, Integer-sided triangles

Example

For n=9 there are A005044(9)=3 integer triangles: [1,4,4], [2,3,4] and [3,3,3]; only one of them is obtuse: 2^2+3^2<16=4^2 and GCD(2,3,4)=1, therefore a(9)=1.

Crossrefs

Cf. A070080, A070081, A070082, A070101, A051493, A070104, A070107, A070084, A070128.

Sequence in context: A114325 A101048 A204389 * A029182 A035373 A240138

Adjacent sequences: A070099 A070100 A070101 * A070103 A070104 A070105

Keyword

nonn

Author

Reinhard Zumkeller, May 05 2002

Status

approved