A120261 - OEIS

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A120261

Number of primitive triangles with integer sides a<=b<=c and inradius n; primitive means gcd(a, b, c) = 1.

1, 4, 10, 11, 13, 28, 17, 26, 31, 31, 20, 77, 28, 46, 67, 40, 28, 100, 26, 72, 120, 62, 32, 139, 44, 53, 71, 118, 32, 202, 35, 70, 135, 73, 97, 211, 33, 80, 130, 134, 36, 284, 45, 141, 183, 78, 50, 226, 68, 112, 150, 146, 38, 173, 150, 219, 182, 80, 38, 468, 36, 82

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

REFERENCES

Mohammad K. Azarian, Circumradius and Inradius, Problem S125, Math Horizons, Vol. 15, Issue 4, April 2008, p. 32. Solution published in Vol. 16, Issue 2, November 2008, p. 32.

LINKS

David W. Wilson, Table of n, a(n) for n = 1..10000

EXAMPLE

a(3)=10 because 10 triangles have coprime integer sides and inradius 3, namely (7,24,25) (7,65,68) (8,15,17) (11,13,20) (12,55,65) (13,40,51) (15,28,41) (16,25,39) (19,20,37) (11,100,109).

CROSSREFS

Cf. A120062, A120252.

See A120062 for sequences related to integer-sided triangles with integer inradius n.

Sequence in context: A102535 A074226 A106631 * A310338 A101154 A182943

Adjacent sequences: A120258 A120259 A120260 * A120262 A120263 A120264

KEYWORD

nonn

AUTHOR

David W. Wilson, Jun 13 2006

STATUS

approved