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 A308026 a(n) = n*(2*n - 3 - (-1)^n)*(11*n + (-1)^n)/24. 0
 0, 0, 16, 30, 90, 134, 266, 356, 588, 740, 1100, 1330, 1846, 2170, 2870, 3304, 4216, 4776, 5928, 6630, 8050, 8910, 10626, 11660, 13700, 14924, 17316, 18746, 21518, 23170, 26350, 28240, 31856, 34000, 38080, 40494, 45066, 47766, 52858, 55860, 61500, 64820 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Total surface area of all rectangular prisms with dimensions s X t X t where s and t are positive integers, n = s + t and s < t. For example, the surface area gives 4*s*t + 2*t^2 = 2*t*(2*s+t). Consider the partitions of n into two distinct parts (s,t) with s < t. Then a(n) is the sum of all the products (2*t)*(2*s+t), using corresponding parts from each (s,t). Also, the total area of all rectangles with dimensions (2*t) X (2*s+t), where s and t are positive integers, n = s + t and s < t. LINKS Table of n, a(n) for n=1..42. Index entries for sequences related to partitions Index entries for linear recurrences with constant coefficients, signature (1,3,-3,-3,3,1,-1). FORMULA G.f.: 2*x^3*(8 + 7*x + 6*x^2 + x^3)/((1 + x)^3*(1 - x)^4). - Bruno Berselli, May 10 2019 a(n) = a(n-1) + 3*a(n-2) - 3*a(n-3) - 3*a(n-4) + 3*a(n-5) + a(n-6) - a(n-7). a(n) = 2 * Sum_{i=1..floor((n-1)/2)} (n - i)*(n + i). MATHEMATICA Table[n*(2*n - 3 - (-1)^n)*(11*n + (-1)^n)/24, {n, 60}] CROSSREFS Sequence in context: A064634 A255265 A183372 * A145581 A186453 A129617 Adjacent sequences: A308023 A308024 A308025 * A308027 A308028 A308029 KEYWORD nonn,easy AUTHOR Wesley Ivan Hurt, May 09 2019 STATUS approved

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Last modified September 15 03:41 EDT 2024. Contains 375931 sequences. (Running on oeis4.)