e28a :: Integer
e28a = 1 + sum [4*(n-2)^2 + 10*(n-1)
               | n <- [3, 5 .. 1001]]


e28b :: Integer
e28b = let n = 500
           sumSquares = n*(n+1)*(2*n+1) `div` 6
           sumLinear = n*(n+1) `div` 2
       in 16*sumSquares + 4*sumLinear + 4*n + 1

λ> :set +s
λ> e28a
669171001
(0.00 secs, 617,688 bytes)

λ> e28b
669171001
(0.00 secs, 82,400 bytes)
λ> 

— Me@2025-11-17 12:00:22 AM

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2025.11.17 Monday (c) All rights reserved by ACHK