#include<stdio.h>
#include<conio.h>
int main()
{
int number, i, sum=0;
clrscr();
printf("Enter number: ");
scanf("%d", &number);
for(i=0;i < number; i++)
{
sum = sum+i;
if(sum == number)
{
printf("%d is TRIANGULAR NUMBER.", number);
break;
}
}
if(number == i)
{
printf("%d is NOT TRIANGULAR NUMBER.", number);
}
getch();
return(0);
}
Output
Run 1:
------------
Enter number: 15 ↲
15 is TRIANGULAR NUMBER.
Run 2:
------------
Enter number: 155 ↲
155 is NOT TRIANGULAR NUMBER.
Run 3:
------------
Enter number: 153 ↲
153 is TRIANGULAR NUMBER.
Run 4:
------------
Enter number: 276 ↲
276 is TRIANGULAR NUMBER.