Question

Write the first four triangular numbers.​

Answer 1

Answer:

0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630, 666... (This sequence is included in the On-Line Encyclopedia of Integer Sequences (sequence A000217 in the OEIS)).

Answer 2

Answer:

Triangular number in above

Step-by-step explanation:

1. 1

2. 3

3. 6

4. 10

5. 15

5. 21