P3C, R5F, T8I, V12L, ?

3 2 3 6 12 37.5 115.5

36 216 64.8 388.8 A 699.84 209.952 A÷36 ?

0 1 9 36 99 225 441

42 3.5 73 26.25 118.125

1 3 9 31 128 651 3913

2 3 5 8 14 23 41 69.

160 80 120 180 1050 4725 25987.5

Three numbers are in G.P. Their sum is 28 and product is 512. The numbers are

The sum of the series: 1² + 2² + 3² + 4² + ……+ 15² is