What is the recursive formula for the sequence #4, 12, 20,...# ?
1 Answer
Feb 22, 2017
Explanation:
As far as it goes, this is an arithmetic sequence with common difference
#12 - 4 = 8#
#20 - 12 = 8#
So we can describe it recursively by:
#{ (a_1 = 4), (a_(n+1) = a_n + 8 " for " n >= 1) :}#
Alternatively, a direct formula is given by:
#a_n = 4 + 8(n-1)#
or if you prefer:
#a_n = 8n - 4#