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A051519
Exactly n integer-sided triangles of perimeter a(n) have integer area.
1
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
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
KEYWORD
nonn
EXTENSIONS
More terms from Randall L Rathbun, Jan 26 2007
STATUS
approved