Question

Fill in the missing number: 2, 8, 27, 85, 260, _, 2365

Answer 1

Each number is mutliplied by 3 and then numbers 2,3,4,5,... are added successively.

2*3+2=8

8*3+3=27

27*3+4=85

85*3+5=260

260*3+6=786

So it's 786.

Btw, the general formula for this sequence is
`a_n=(1)/(12)(-6n+13\cdot3^n-9)`