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What is that mysterious diagonal sum sequence though? Here is cracking of that mystery, apparently the points that make up each sum-sequence take on a family of parabolic curves of the form "Rx(i)= -2i^2 + (x+3)i - x" where the number of positive integer values for each curve goes from "i=1" to "i=(x+(1+(-1)^(x+1))/2)/2", and each sequential diagonal sum is the summation for Rx(i) over the range of "i" for each Matrix row "Rx" pertaining to each parabola within the family of parabolas.
The thing that caught my eye about that sum of diagonals of dot pyramid sequence (SDDP) is that it looks similar to the Fibonacci sequence (1,1,2,3,5,8,13,21...) except that it diverges short of that sequence after 8... "SDDP = (1,1,2,3,5,8,12,18,25,35,46,...)", so just for curiosity sake I decided to graph this lesser known spiral out on Excell:
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