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.

Showing 1-3 of 3 results.

A125750 A Moessner triangle using (1, 3, 5, ...).

Original entry on oeis.org

1, 3, 5, 10, 19, 11, 42, 89, 64, 19, 216, 498, 415, 160, 29, 1320, 3254, 3023, 1385, 335, 41, 9360, 24372, 24640, 12803, 3745, 623, 55, 75600, 206100, 223116, 127799, 42938, 8750, 1064, 71, 685440, 1943568, 2227276, 1380076, 516201, 122010, 18354, 1704
Offset: 1

Views

Author

Gary W. Adamson, Dec 06 2006

Keywords

Comments

Right border of the triangle = A028387, left border = A007680.

Examples

			Circling the 1, 3, 6, ...(-th) terms in the sequence (1, 3, 5, 7, ...), we get A018387: (1, 5, 11, 19, 29, ...). Taking partial sums of the remaining terms, we get (3, 10, 19, 32, ...) in row 2 and we circle 3 and 19. In row 3 we circle the 10.
First few rows of the triangle are:
    1;
    3,   5;
   10,  19,  11;
   42,  89,  64,  19;
  216, 498, 415, 160,  29;
  ...
		

References

  • J. H. Conway and R. K. Guy, "The Book of Numbers", Springer-Verlag, 1996, pp. 63-64.

Crossrefs

Formula

Using "Moessner's Magic" (Conway and Guy, pp. 63-64; cf. A125714), we circle the 1, 3, 6, 10, ...(-th) terms in the sequence (1, 3, 5, 7, ...) and take partial sums of the remaining terms, making row 2. Circle the terms in row 2 one place offset to the left of row 1 terms, then take partial sums. Continue with analogous operations for succeeding rows. The triangle = leftmost circled terms in each row.

Extensions

More terms from Joshua Zucker, Jun 17 2007

A132787 Triangle read by rows: T(n,k) = 2*A001263(n,k) - 1.

Original entry on oeis.org

1, 1, 1, 1, 5, 1, 1, 11, 11, 1, 1, 19, 39, 19, 1, 1, 29, 99, 99, 29, 1, 1, 41, 209, 349, 209, 41, 1, 1, 55, 391, 979, 979, 391, 55, 1, 1, 71, 671, 2351, 3527, 2351, 671, 71, 1, 1, 89, 1079, 5039, 10583, 10583, 5039, 1079, 89, 1, 1, 109, 1649, 9899, 27719, 38807, 27719, 9899, 1649, 109, 1
Offset: 1

Views

Author

Gary W. Adamson, Aug 30 2007

Keywords

Examples

			First few rows of the triangle are:
  1;
  1, 1;
  1, 5, 1;
  1, 11, 11, 1;
  1, 19, 39, 19, 1;
  1, 29, 99, 99, 29, 1;
  ...
		

Crossrefs

Column 2 is A018387.
Row sums are A132788.
Cf. A001263.

Programs

  • PARI
    T(n,k) = if(k<=n, 2*binomial(n-1, k-1) * binomial(n, k-1) / k - 1, 0); \\ Andrew Howroyd, Aug 10 2018

Formula

Equals 2*A001263 - A000012 as infinite lower triangular matrices; where A001263 = the Narayana triangle.
T(n,k) = 2*binomial(n-1, k-1) * binomial(n, k-1) / k - 1. - Andrew Howroyd, Aug 10 2018

Extensions

a(20) corrected and terms a(56) and beyond from Andrew Howroyd, Aug 10 2018

A130299 A130296 * A051340.

Original entry on oeis.org

1, 3, 2, 5, 3, 3, 7, 4, 4, 4, 9, 5, 5, 5, 5, 11, 6, 6, 6, 6, 6, 13, 7, 7, 7, 7, 7, 7, 15, 8, 8, 8, 8, 8, 8, 8, 17, 9, 9, 9, 9, 9, 9, 9, 9, 19, 10, 10, 10, 10, 10, 10, 10, 10, 10
Offset: 1

Views

Author

Gary W. Adamson, May 20 2007

Keywords

Comments

Row sums = A018387: (1, 5, 11, 19, 29, 41, 55, ...).

Examples

			First few rows of the triangle:
   1;
   3, 2;
   5, 3, 3;
   7, 4, 4, 4;
   9, 5, 5, 5, 5;
  11, 6, 6, 6, 6, 6;
  13, 7, 7, 7, 7, 7, 7;
  ...
		

Crossrefs

Formula

A130296 * A051340 as infinite lower triangular matrices.
Showing 1-3 of 3 results.