A145356 - OEIS

%I #15 Oct 02 2024 07:54:08

%S 1,6,1,42,6,1,336,42,36,6,1,3024,336,252,42,36,6,1,30240,3024,2016,

%T 1764,336,252,216,42,36,6,1,332640,30240,18144,14112,3024,2016,1764,

%U 1512,336,252,216,42,36,6,1,3991680,332640,181440,127008,112896,30240,18144,14112

%N Partition number array, called M31hat(6).

%C Each partition of n, ordered like in Abramowitz-Stegun (A-St order; for the reference see A134278), is mapped to a nonnegative integer a(n,k) =: M31hat(6;n,k) with the k-th partition of n in A-St order.

%C The sequence of row lengths is A000041 (partition numbers) [1, 2, 3, 5, 7, 11, 15, 22, 30, 42,...].

%C Sixth member (K=6) in the family M31hat(K) of partition number arrays.

%C If M31hat(6;n,k) is summed over those k numerating partitions with fixed number of parts m one obtains the unsigned triangle S1hat(6):= A145357.

%H W. Lang, <a href="/A145356/a145356.txt">First 10 rows of the array and more.</a>

%H W. Lang, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL12/Lang/lang.html">Combinatorial Interpretation of Generalized Stirling Numbers</a>, J. Int. Seqs. Vol. 12 (2009) 09.3.3.

%F a(n,k) = product(|S1(6;j,1)|^e(n,k,j),j=1..n) with |S1(6;n,1)| = A049374(n,1) = A001725(n+4) = [1,6,42,336,3024,30240,332640,...] = (n+4)!/5!, n>=1 and the exponent e(n,k,j) of j in the k-th partition of n in the A-St ordering of the partitions of n.

%e [1];[6,1];[42,6,1];[336,42,36,6,1];[3024,336,252,42,36,6,1];...

%e a(4,3)= 36 = |S1(6;2,1)|^2. The relevant partition of 4 is (2^2).

%Y Cf. A145358 (row sums).

%Y Cf. A144890 (M31hat(5) array), A145357 (S1hat(6)).

%K nonn,easy,tabf

%O 1,2

%A _Wolfdieter Lang_ Oct 17 2008, Oct 28 2008