

A334289


Sum of the lengths of all r X s rectangles such that r < s, r + s = 2n and (s  r)  (s * r).


0



0, 0, 4, 6, 6, 8, 8, 22, 22, 12, 12, 68, 14, 16, 78, 62, 18, 44, 20, 104, 104, 24, 24, 234, 56, 28, 94, 140, 30, 156, 32, 158, 156, 36, 178, 326, 38, 40, 182, 372, 42, 208, 44, 212, 400, 48, 48, 638, 106, 112, 234, 248, 54, 188, 262, 496, 260, 60, 60, 1040
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OFFSET

1,3


LINKS



FORMULA

a(n) = Sum_{i=1..n1} (2*ni) * (1  ceiling(i*(2*ni)/(2*n2*i)) + floor(i*(2*ni)/(2*n2*i))).


EXAMPLE

a(8) = 22; 2*8 = 16 has two rectangles, 4 X 12 and 6 X 10, such that (12  4)  (12 * 4) = 8  48 and (10  6)  (10 * 6) = 4  60. The sum of the lengths of the rectangles is 12 + 10 = 22.


MATHEMATICA

Table[Sum[(2 n  i) (1  Ceiling[(i (2 n  i))/(2 n  2 i)] + Floor[(i (2 n  i))/(2 n  2 i)]), {i, n  1}], {n, 80}]


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



