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 A306656 Number of ways to fill a 3D matrix with n distinct values. 0
 1, 1, 6, 18, 144, 360, 6480, 15120, 403200, 2177280, 32659200, 119750400, 8622028800, 18681062400, 784604620800, 11769069312000, 313841848320000, 1067062284288000, 115242726703104000, 364935301226496000, 43792236147179520000, 459818479545384960000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS This sequence is a generalization of A323295 to the 3D case. Usually, in multidimensional data related applications (i.e., images, MRI), data is vectorized and then processed. However, because of vectorization, the spatial information in the data is lost. This reverse mapping shows the possible number of spatial states the original data could have been in. LINKS Table of n, a(n) for n=0..21. FORMULA a(n) = A007425(n) * n! for n > 0, a(0) = 1. EXAMPLE For n = 6, a(6) = 6480, A007425(6) = 9 namely there are 9 ways to arrange 6 voxels into a 3D matrix: [1,1,6], [1,6,1], [6,1,1], [2,3,1], [3,2,1], [2,1,3], [3,1,2], [1,2,3], [1,3,2]. Then there are 6! ways to fill it with the numbers. 9*6! = 6480. MAPLE with(numtheory): a:= n-> `if`(n=0, 1, add(tau(d), d=divisors(n))*n!): seq(a(n), n=0..23); # Alois P. Heinz, Mar 03 2019 CROSSREFS Cf. A007425, A077592, A323295. Sequence in context: A222913 A091054 A012774 * A027744 A196868 A077531 Adjacent sequences: A306653 A306654 A306655 * A306657 A306658 A306659 KEYWORD nonn AUTHOR Yigit Oktar, Mar 03 2019 EXTENSIONS More terms from Alois P. Heinz, Mar 03 2019 STATUS approved

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Last modified May 26 04:31 EDT 2024. Contains 372807 sequences. (Running on oeis4.)