152981

Our solution:
Choose any two consecutive numbers from the Fibonacci Sequence and multiply by two, like this:

1+1=2 x 2=4
1+2=3 x 2=6
2+3=5 x 2=10
3+5=8 x 2=16
5+8=13 x 2=26
8+13=21 x 2=42
13+21=34 x 2=68
...
These answers are the same as the sum of adding together any three consecutive numbers, like so:

1+1+2= 4
1+2+3= 6
2+3+5= 10
3+5+8= 16
5+8+13= 26
8+13+21= 42
13+21+34= 68

To conclude, adding any three consecutive numbers together is the equivalent of adding any two consecutive numbers together and multiplying by two.