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 A144886 Lower triangular array called S1hat(4) related to partition number array A144885. 5
 1, 4, 1, 20, 4, 1, 120, 36, 4, 1, 840, 200, 36, 4, 1, 6720, 1720, 264, 36, 4, 1, 60480, 12480, 2040, 264, 36, 4, 1, 604800, 118560, 16000, 2296, 264, 36, 4, 1, 6652800, 1081920, 149600, 17280, 2296, 264, 36, 4, 1, 79833600, 11793600, 1362240, 163680, 18304, 2296, 264 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If in the partition array M31hat(4):=A144885 entries with the same parts number m are summed one obtains this triangle of numbers S1hat(4). In the same way the signless Stirling1 triangle |A008275| is obtained from the partition array M_2 = A036039. The first columns are A001715(n+2), A144888, A144889,... LINKS Table of n, a(n) for n=1..52. W. Lang, First 10 rows of the array and more. W. Lang, Combinatorial Interpretation of Generalized Stirling Numbers, J. Int. Seqs. Vol. 12 (2009) 09.3.3. FORMULA a(n,m)=sum(product(|S1(4;j,1)|^e(n,m,q,j),j=1..n),q=1..p(n,m)) if n>=m>=1, else 0. Here p(n,m)=A008284(n,m), the number of m parts partitions of n and e(n,m,q,j) is the exponent of j in the q-th m part partition of n. |S1(4,n,1)|= A049352(n,1) = A001715(n+2) = (n+2)!/3!. EXAMPLE [1];[4,1];[20,4,1];[120,36,4,1];[840,200,36,4,1];... CROSSREFS A144887 (row sums). Sequence in context: A333273 A128041 A144885 * A117380 A185420 A167432 Adjacent sequences: A144883 A144884 A144885 * A144887 A144888 A144889 KEYWORD nonn,easy,tabl AUTHOR Wolfdieter Lang Oct 09 2008 STATUS approved

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Last modified December 2 13:30 EST 2023. Contains 367524 sequences. (Running on oeis4.)