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A152421
a(n) = binomial(A000290(n), A006218(n)).
1
1, 4, 126, 12870, 3268760, 3796297200, 3348108992991, 19619725782651120, 95399637739311016800, 1917353200780443050763600, 7359958875023243471254188840, 3720132147124647210937719983999040
OFFSET
1,2
COMMENTS
This sequence counts combinations that are possible to create by moving around the numbers in A051731. It would be interesting to know what values the determinant can take for such combinations.
MAPLE
A000290 := proc(n) n^2 ; end: A006218 := proc(n) local k ; add( floor(n/k), k=1..n) ; end: A152421 := proc(n) binomial(A000290(n), A006218(n)) ; end: for n from 1 to 30 do printf("%d, ", A152421(n)) ; od: # R. J. Mathar, Jan 22 2009
CROSSREFS
Sequence in context: A054053 A348814 A070781 * A270959 A291851 A128790
KEYWORD
nonn
AUTHOR
Mats Granvik, Dec 03 2008
EXTENSIONS
Terms beyond a(5) from R. J. Mathar, Jan 22 2009
STATUS
approved