A177063 Number of Pythagorean triangles with area n.

0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1

Offset

1,210

Comments

The first term > 1 is a(210) = 2, cf. A009127, A055193 and A024407. Up to there the sequence coincides with the characteristic function of A009112. The triangles are not necessarily primitive.

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries related to Pythagorean triples.

Prog

(PARI) a(n)=my(N=1+#n=divisors(2*n)); sum(i=1, N\2, issquare(n[i]^2+n[N-i]^2));

Crossrefs

Cf. A009111, A009127, A177021.

Sequence in context: A011682 A185015 A318880 * A341619 A302049 A078926

Adjacent sequences: A177060 A177061 A177062 * A177064 A177065 A177066

Keyword

nonn

Author

M. F. Hasler, Dec 09 2010

Extensions

Secondary offset added by Antti Karttunen, Nov 24 2017

Status

approved