Notice that the difference between each term is 4
#5-1=4#
#9-5=4#
#13-9=4# and so on
Lets look at how the numbers grow
The first number (term) is 1
# 1+0=1 #
#1+4=5#
#1+4+4=9#
#1+4+4+4=13#
#1+4+4+4+4=17#
Now lets look at these by position in the sequence
Note that I am using the identifiers of type #a_i# for each row
#[("Position" ," | ", "Structure"," | ", "Final value"),(1 ->a_1, " | ",1+0color(white)("ddddddddddd")," | ", 1),(2->a_2," | ",1+4color(white)("ddddddddddd")," | ",5),( 3->a_3," | ",1+4+4color(white)("dddddddd")," | ",9 ) ,(4->a_4," | ",1+4+4+4color(white)("ddddd")," | ",13) ,(5->a_5," | ",1+4+4+4+4color(white)("dd")," | ",17) ]#
Count the 4's in each row
Notice that there is 1 less than the row number
Extending this suppose there was an #n^("th")# row then the final value for that row would be
#1+4(n-1)#
So for the 15th row we substitute 15 for n giving
#a_15=1+4(15-1)#
#a_15=1+(4xx14)#
#a_15=1+color(white)("dd")56color(white)("ddd") = 57#
