yogi_Compute Row By Row Average Considering Every Nth Column of An Open Ended Range

                                          Google Spreadsheet   Post  #956

Yogi Anand, D.Eng, P.E.      ANAND Enterprises LLC -- Rochester Hills MI     www.energyefficientbuild.com.    Jan 05, 2013

user collin.m.barrett said:(http://productforums.google.com/forum/?zx=6xwd73m1l93e#!category-topic/docs/spreadsheets/0StscdBKHo0)
SELECT every nth cell in a row 

I am using equations similar to the following to select the values in every 5th column of a given row. Is there a way to do this dynamically rather than typing in each individual cell reference? Thanks.

=AVERAGE(N4,S4,X4,AC4,AH4,AM4,AR4,AW4,BB4,BG4,BL4,BQ4,BV4,CA4,CF4,CK4,CP4,CU4,CZ4,DE4,DJ4,DO4,DT4,DY4,ED4,EI4,EN4,ES4,EX4,FC4)

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following is a solution to a bit more generalized proble