Question

What is the pattern in the sequence 1, 3, 4, 7, 6, 12, 8, 15, 13, ??

Answer 1

This is the sequence A000203 - the sum of the divisors of `n`

See https://oeis.org/A000203

Explanation:

`1 = 1`
`3 = 1 + 2`
`4 = 1 + 3`
`7 = 1 + 2 + 4`
`6 = 1 + 5`
`12 = 1+2+3+6`
`8 = 1+7`
`15 = 1+2+4+8`
`13=1+3+9`