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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 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=1..12.

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: A178842 A054053 A070781 * A270959 A291851 A128790

Adjacent sequences:  A152418 A152419 A152420 * A152422 A152423 A152424

KEYWORD

nonn

AUTHOR

Mats Granvik, Dec 03 2008

EXTENSIONS

Terms beyond a(5) from R. J. Mathar, Jan 22 2009

STATUS

approved

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Last modified July 24 23:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)