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A077592
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Table by antidiagonals of tau_k(n), the k-th Piltz function (see A007425), or n-th term of the sequence resulting from applying the inverse Möbius transform (k-1) times to the all-ones sequence.
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23
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1, 1, 1, 1, 2, 1, 1, 3, 2, 1, 1, 4, 3, 3, 1, 1, 5, 4, 6, 2, 1, 1, 6, 5, 10, 3, 4, 1, 1, 7, 6, 15, 4, 9, 2, 1, 1, 8, 7, 21, 5, 16, 3, 4, 1, 1, 9, 8, 28, 6, 25, 4, 10, 3, 1, 1, 10, 9, 36, 7, 36, 5, 20, 6, 4, 1, 1, 11, 10, 45, 8, 49, 6, 35, 10, 9, 2, 1, 1, 12, 11, 55, 9, 64, 7, 56, 15, 16, 3, 6, 1
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OFFSET
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1,5
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COMMENTS
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As an array with offset n=0, k=1, also the number of length n chains of divisors of k. - Gus Wiseman, Aug 04 2022
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LINKS
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FORMULA
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If n = Product_i p_i^e_i, then T(n,k) = Product_i C(k+e_i-1, e_i). T(n,k) = sum_d{d|n} T(n-1,d) = A077593(n,k) - A077593(n-1,k).
Columns are multiplicative.
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EXAMPLE
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T(6,3) = 9 because we have: 1*1*6, 1*2*3, 1*3*2, 1*6*1, 2*1*3, 2*3*1, 3*1*2, 3*2*1, 6*1*1. - Geoffrey Critzer, Feb 16 2015
Array begins:
k=1 k=2 k=3 k=4 k=5 k=6 k=7 k=8
n=0: 1 1 1 1 1 1 1 1
n=1: 1 2 2 3 2 4 2 4
n=2: 1 3 3 6 3 9 3 10
n=3: 1 4 4 10 4 16 4 20
n=4: 1 5 5 15 5 25 5 35
n=5: 1 6 6 21 6 36 6 56
n=6: 1 7 7 28 7 49 7 84
n=7: 1 8 8 36 8 64 8 120
n=8: 1 9 9 45 9 81 9 165
The triangular form T(n,k) = A(n-k,k) gives the number of length n - k chains of divisors of k. It begins:
1
1 1
1 2 1
1 3 2 1
1 4 3 3 1
1 5 4 6 2 1
1 6 5 10 3 4 1
1 7 6 15 4 9 2 1
1 8 7 21 5 16 3 4 1
1 9 8 28 6 25 4 10 3 1
1 10 9 36 7 36 5 20 6 4 1
1 11 10 45 8 49 6 35 10 9 2 1
(End)
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MAPLE
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with(numtheory):
A:= proc(n, k) option remember; `if`(k=1, 1,
add(A(d, k-1), d=divisors(n)))
end:
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MATHEMATICA
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tau[n_, 1] = 1; tau[n_, k_] := tau[n, k] = Plus @@ (tau[ #, k - 1] & /@ Divisors[n]); Table[tau[n - k + 1, k], {n, 14}, {k, n, 1, -1}] // Flatten (* Robert G. Wilson v *)
tau[1, k_] := 1; tau[n_, k_] := Times @@ (Binomial[Last[#] + k - 1, k - 1] & /@ FactorInteger[n]); Table[tau[k, n - k + 1], {n, 1, 13}, {k, 1, n}] // Flatten (* Amiram Eldar, Sep 13 2020 *)
Table[Length[Select[Tuples[Divisors[k], n-k], And@@Divisible@@@Partition[#, 2, 1]&]], {n, 12}, {k, 1, n}] (* TRIANGLE, Gus Wiseman, May 03 2021 *)
Table[Length[Select[Tuples[Divisors[k], n-1], And@@Divisible@@@Partition[#, 2, 1]&]], {n, 6}, {k, 6}] (* ARRAY, Gus Wiseman, May 03 2021 *)
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CROSSREFS
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Columns include (with multiplicity and some offsets) A000012, A000027, A000027, A000217, A000027, A000290, A000027, A000292, A000217, A000290, A000027, A002411, A000027, A000290, A000290, A000332 etc.
The diagonal n = k of the array (central column of the triangle) is A163767.
The transpose of the array is A334997.
Diagonal n = k of the array is A343939.
Antidiagonal sums of the array (or row sums of the triangle) are A343940.
A067824(n) counts strict chains of divisors starting with n.
A074206(n) counts strict chains of divisors from n to 1.
A146291(n,k) counts divisors of n with k prime factors (with multiplicity).
A251683(n,k) counts strict length k + 1 chains of divisors from n to 1.
A253249(n) counts nonempty chains of divisors of n.
A334996(n,k) counts strict length k chains of divisors from n to 1.
A337255(n,k) counts strict length k chains of divisors starting with n.
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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