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A204464
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Number of 2*n-element subsets that can be chosen from {1,2,...,16*n} having element sum n*(16*n+1).
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1
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1, 8, 790, 148718, 35154340, 9408671330, 2725410001024, 834014033203632, 265724127467961324, 87318355216835049968, 29402690636348418710858, 10098693807141197229592054, 3525753285145412581617963136, 1248001014165722671454730108968, 446964111600452023289482445527716
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OFFSET
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0,2
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COMMENTS
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a(n) is the number of partitions of n*(16*n+1) into 2*n distinct parts <=16*n.
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LINKS
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Table of n, a(n) for n=0..14.
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EXAMPLE
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a(1) = 8 because there are 8 2-element subsets that can be chosen from {1,2,...,16} having element sum 17: {1,16}, {2,15}, {3,14}, {4,13}, {5,12}, {6,11}, {7,10}, {8,9}.
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MAPLE
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b:= proc(n, i, t) option remember;
`if` (i<t or n<t*(t+1)/2 or n>t*(2*i-t+1)/2, 0,
`if` (n=0, 1, b(n, i-1, t) +`if`(n<i, 0, b(n-i, i-1, t-1))))
end:
a:= n-> b(n*(16*n+1), 16*n, 2*n):
seq (a(n), n=0..10);
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CROSSREFS
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Bisection of row n=8 of A204459.
Sequence in context: A184974 A060183 A145415 * A001547 A168310 A220186
Adjacent sequences: A204461 A204462 A204463 * A204465 A204466 A204467
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KEYWORD
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nonn
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AUTHOR
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Alois P. Heinz, Jan 18 2012
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STATUS
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approved
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