Practice problem
A sequence is given by 0,1,3,6,10,⋯0,1,3,6,10,\cdots0,1,3,6,10,⋯ where n≥1n\ge1n≥1. Write this as a recursive sequence.
an=an−1−na_n =a_{n-1}-nan=an−1−n
an=an−1−(n−1)a_n =a_{n-1}-(n-1)an=an−1−(n−1)
an=an−1+na_n =a_{n-1}+nan=an−1+n
an=an−1+(n−1)a_n =a_{n-1}+(n-1)an=an−1+(n−1)
Type a concept, like “slope” or “photosynthesis”.