The question is mis worded. A sequence is a list of numbers that follows some rule. A series is the sum of a sequence.
An arithmetic sequence has the same number added to each previous number to arrive at the next number. The sum of such a sequence is the sum of the terms.
Pick some number to add to each term. The easiest is 1.
n, n+1, n+2, n+3, n+4, n+5, n+6 is an arithmetic series in which 1 is added to each number to arrive at the next number in the sequence.
The sum is n + n+1 + n+2 + n+3 + n+4 + n+5 + n+6 and it must = 64.
n + n+1 + n+2 + n+3 + n+4 + n+5 + n+6 = 64
7n + 21=64
7n = 43
n = 43/7
The sequence is 43/7, 50/7, 57/7, 64/7, 71/7, 78/7, 85/7