cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A038675 Triangle read by rows: T(n,k)=A(n,k)*binomial(n+k-1,n), where A(n,k) are the Eulerian numbers (A008292).

Original entry on oeis.org

1, 1, 3, 1, 16, 10, 1, 55, 165, 35, 1, 156, 1386, 1456, 126, 1, 399, 8456, 25368, 11970, 462, 1, 960, 42876, 289920, 393030, 95040, 1716, 1, 2223, 193185, 2577135, 7731405, 5525091, 741741, 6435, 1, 5020, 803440, 19411480, 111675850, 176644468
Offset: 1

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Comments

Andrews, Theory of Partitions, (1976), discussion of multisets.
Let a = a_1,a_2,...,a_n be a sequence on the alphabet {1,2,...,n}. Scan a from left to right and create an n-permutation by noting the POSITION of the elements as you come to them in order from least to greatest. See example. T(n,k) is the number of sequences that correspond to such a permutation having exactly n-k descents. [From Geoffrey Critzer, May 19 2010]

Examples

			1;
1,3;
1,16,10;
1,55,165,35;
1,156,1386,1456,126;
...
If a = 3,1,1,2,4,3 the corresponding 6-permutation is 2,3,4,1,6,5 because the first 1 is in the 2nd position, the second 1 is in the 3rd position,the 2 is in the 4th position, the first 3 is in the first position, the next 3 is in the 6th position and the 4 is in the 5th position of the sequence a. [From _Geoffrey Critzer_, May 19 2010]
		

References

  • R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics, 2nd edition, Addison-Wesley, Reading, Mass., 1994, p. 269 (Worpitzky's identity).
  • Miklos Bona, Combinatorics of Permutations,Chapman and Hall,2004,page 6. [From Geoffrey Critzer, May 19 2010]

Crossrefs

Row sums yield A000312 (Worpitzky's identity).
Cf. A008292.

Programs

  • Maple
    A:=(n,k)->sum((-1)^j*(k-j)^n*binomial(n+1,j),j=0..k): T:=(n,k)->A(n,k)*binomial(n+k-1,n): seq(seq(T(n,k),k=1..n),n=1..10);
  • Mathematica
    Table[Table[Eulerian[n, k] Binomial[n + k, n], {k, 0, n - 1}], {n, 1,10}] (* Geoffrey Critzer, Jun 13 2013 *)

Extensions

More terms from Emeric Deutsch, May 08 2004

A014732 Squares of numbers in triangle of Eulerian numbers that are not 1.

Original entry on oeis.org

16, 121, 121, 676, 4356, 676, 3249, 91204, 91204, 3249, 14400, 1418481, 5837056, 1418481, 14400, 61009, 18429849, 243953161, 243953161, 18429849, 61009, 252004, 213393664, 7785238756, 24395316100, 7785238756, 213393664, 252004
Offset: 1

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Formula

a(n) = A014449(n)^2. - Sean A. Irvine, Nov 18 2018

Extensions

More terms from James Sellers
Offset corrected by Joerg Arndt, Nov 19 2018
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