A051519 Exactly n integer-sided triangles of perimeter a(n) have integer area.

12, 32, 48, 36, 64, 98, 160, 84, 128, 168, 144, 108, 416, 196, 192, 216, 288, 256, 780, 336, 294, 612, 396, 378, 1026, 392, 448, 420, 512, 324, 600, 792, 800, 432, 484, 540, 1000, 810, 676, 576, 1760, 2842, 1250, 648, 726, 924, 980, 2484, 1134, 864, 1210, 784

Offset

1,1

Links

Randall L Rathbun, Table of n, a(n) for n = 1..229

Prog

(C)
#include <stdio.h> /* printf() */ #include <math.h> /* sqrt() round() */
unsigned int is_triangle(int a, int b, int c) { double s, A, B; s = (a+b+c)/2.0; A = s*(s-a)*(s-b)*(s-c); B = floor(sqrt(A)+0.1); if ( B*B == A && A > 0.0 ) return 1; else return 0; }
int main() { int set; int a, b, c, p; for (p=1; p<15001; p++) { printf("%d ", p); set = 0; for (a=1; a<p; a++) { for (b=a; b<p; b++) { c = p-a-b; if (c >=b && c < a+b && b < a+c && a < b+c ) { if (is_triangle(a, b, c)) { set += 1; printf("[%d %d %d] ", a, b, c); } } } } printf(" "); printf("perimeter %d = %d ", p, set); } return 0; } /* Randall L Rathbun, Jan 26 2007 */

Crossrefs

Sequence in context: A118785 A071336 A248817 * A305074 A166959 A134582

Adjacent sequences: A051516 A051517 A051518 * A051520 A051521 A051522

Keyword

nonn

Author

David W. Wilson

Extensions

More terms from Randall L Rathbun, Jan 26 2007

Status

approved