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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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
FORMULA
a(n) = Sum_{i=1..n-1} (2*n-i) * (1 - ceiling(i*(2*n-i)/(2*n-2*i)) + floor(i*(2*n-i)/(2*n-2*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
Cf. A333754.
Sequence in context: A111653 A372786 A228363 * A173395 A305317 A049089
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 23 2020
STATUS
approved

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Last modified May 18 19:36 EDT 2024. Contains 372666 sequences. (Running on oeis4.)