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A071764
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Number of minimal rectangular envelopes (up to rotation) that enclose n contiguous squares.
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0
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1, 1, 2, 3, 4, 6, 8, 11, 14, 17, 21, 26, 30, 36, 42, 48, 54, 62, 69, 78, 86, 95, 105, 116, 125, 136, 148, 160, 172, 186, 198, 213, 227, 242, 258, 274, 288, 306, 324, 342, 359, 379, 397, 418, 438, 458, 480, 503, 523, 546, 569, 593, 617, 643, 667, 693, 718, 745
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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LINKS
| K. S. Brown, More info
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FORMULA
| a(n)=(1/2)*( A000217(n) + A008619(n)- A000196(n-1) - A006218(n-1) ) Recurrence : a(n) = a(n-1) + {n/2} - {tau(n-1)/2} where {x} signifies the least integer greater than or equal to x, tau(x) the number of divisors of x.
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PROG
| (PARI) for(n=1, 100, print1(1/2*(n*(n+1)/2+floor((n+1)/2)-floor(sqrt(n-1))-sum(i=1, n, floor((n-1)/i))), ", "))
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CROSSREFS
| Sequence in context: A105799 A102463 A056829 * A059291 A177339 A075535
Adjacent sequences: A071761 A071762 A071763 * A071765 A071766 A071767
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 04 2002
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