First I found the differences 2,12,36,80 I subtracted the squares 1,4,9,16 from those differences 1,8,27,64 I recognized those as the cubes. So to get the next term, we add the square and the cube of the number of the term The recursion formula is an+1 = an + n2 + n3, a1 = 1 ------------------- Start with 1 Add 12+13, which is 1+1=2, get 3 Add 22+23, which is 4+8=12, get 15 Add 32+33, which is 9+27=36, get 51 Add 42+43, which is 16+64=80, get 131 Add 52+53, which is 25+125=150, get 281 Edwin