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Search: id:A136301
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| A136301 |
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Frequency of occurrence for each possible probability of all outcomes for a Secret Santa drawing in which each person draws a name in sequence but is not allowed to pick his own name, and for which the last person does draw his own name. |
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+0 1
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| 1, 1, 1, 1, 5, 2, 1, 1, 13, 6, 13, 2, 6, 2, 1, 1, 29, 14, 73, 6, 42, 18, 29, 2, 18, 8, 14, 2, 6, 2, 1, 1, 61, 30, 301, 14, 186, 86, 301, 6, 102, 48, 186, 18, 102, 42, 61, 2, 42, 20, 86, 8, 48, 20, 30, 2, 18, 8, 14, 2, 6, 2, 1, 1, 125, 62, 1081, 30, 690, 330, 2069, 14, 414, 200, 1394
(list; table; graph; listen)
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OFFSET
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1,5
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COMMENT
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I find it more useful to draw the table as columns instead of rows, where each column has 2^(column-1) rows. This table has a huge number of fascinating properties. I'll list a few here, but would like to add more: Each column shows most numbers in pairs, where the row of the paired number can be found by starting with the row number (starting with 0), converting to binary of a length determined by the column (power of 2), doing a one's compliment, and reversing the order of bits to determine the row number for the paired entry. So in the {1,13,6,13,2,6,2,1} column, row pairs are 001/011 (two 13's), 010/101 (two 6's), 000 / 111 (two 1's) and 100 / 110 (two 2's). In alternating columns, that leaves some "pairs" which map to themselves. The largest of these form a sequence, aka A048144. Graphed, subsequent columns show a fractal pattern. The rows of the table also convert neatly to another fascinating sequence, via the inverse stirling transform. Another conversion
(details later) describes the rows as a series of equations, the coefficients of which again embody this very H() table. (Amazing.) There are a huge number of simple relationships, such as every 4th term in a column is the sum of twice the number below it plus the one above. FYI, I figured this all out by calculating the table explicitly, and then staring at it for years. There's lots more to disclose, but I could use some guidance on how to proceed.
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LINKS
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Brian Parsonnet (bparsonnet(AT)comcast.net), Mar 22 2008, Table of n, a(n) for n = 1..255
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FORMULA
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H(r,c) = sum of H(T(r),L(r)+j) * M(c-T(r)-1,j) for j = 0..c-L(r)-1, where M(y,z) = binomial distribution (y,z) when y - 1 > z, and (y,z)-1 when (y-1)<=z, and T(r) = A053645, and L(r) = A000523.
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EXAMPLE
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For 5 people, there are 9 target outcomes for which the last person gets his own name. But these 9 outcomes share only 4 possible probabilities, namely, 12/576, 8/576, 9/576, and 6/576. For the 9 outcomes, they distribute over these 4 probabilities with the distribution 1, 5, 2, 1 for a total likelihood of 76/576. As to the calculation of the table itself, look at H(3,5) which has the unique value of 73. The final step in the formula described is the dot product of two vectors: {0, 1, 5, 13} * {1, 4, 6, 3} = 73. {1,4,6,3} is almost the binomial distribution for 4 items, but the case (4,3) is 3 instead of 4 (as described by the formula).
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CROSSREFS
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Adjacent sequences: A136298 A136299 A136300 this_sequence A136302 A136303 A136304
Sequence in context: A085119 A010128 A029764 this_sequence A132690 A089086 A038631
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KEYWORD
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uned,nonn,tabl
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AUTHOR
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Brian Parsonnet (bparsonnet(AT)comcast.net), Mar 22 2008
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