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.

A103284 Triangle, read by rows, where row n+1 is formed by sorting, in ascending order, the result of the convolution of row n with {1,1}.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 2, 2, 3, 1, 3, 3, 4, 5, 1, 4, 5, 6, 7, 9, 1, 5, 9, 9, 11, 13, 16, 1, 6, 14, 16, 18, 20, 24, 29, 1, 7, 20, 29, 30, 34, 38, 44, 53, 1, 8, 27, 49, 53, 59, 64, 72, 82, 97, 1, 9, 35, 76, 97, 102, 112, 123, 136, 154, 179, 1, 10, 44, 111, 173, 179, 199, 214, 235, 259
Offset: 0

Views

Author

Paul D. Hanna, Jan 28 2005

Keywords

Comments

Main diagonal is A103285.

Examples

			Convolution of row 5 {1,4,5,6,7,9} with {1,1} = {1,5,9,11,13,16,9}; sort to obtain row 6: {1,5,9,9,11,13,16}.
Rows begin:
1,
1,1,
1,1,2,
1,2,2,3,
1,3,3,4,5,
1,4,5,6,7,9,
1,5,9,9,11,13,16,
1,6,14,16,18,20,24,29,
1,7,20,29,30,34,38,44,53,
1,8,27,49,53,59,64,72,82,97,
1,9,35,76,97,102,112,123,136,154,179,...
		

Crossrefs

Cf. A103285.
Cf. A000079 (row sums), A257641 (central terms), A257646, A107430.

Programs

  • Haskell
    import Data.List (sort)
    a103284 n k = a103284_tabl !! n !! k
    a103284_row n = a103284_tabl !! n
    a103284_tabl = iterate (\xs -> sort $ zipWith (+) (xs++[0]) ([0]++xs)) [1]
    -- Reinhard Zumkeller, Nov 19 2015
  • PARI
    {T(n,k)=local(A=vector(n+1,i,vector(i)),B);A[1][1]=1; for(k=1,n,B=vector(k+1);B[1]=1;B[k+1]=A[k][k]; for(i=2,k,B[i]=A[k][i]+A[k][i-1]); A[k+1]=vecsort(B));return(A[n+1][k+1])}
    

Formula

Row(n+1) = union of {1} and {T(n,k-1) + T(n,k): k=1..n}, sorted in ascending order. - Reinhard Zumkeller, Nov 19 2015

A257641 Central terms of triangle A103284.

Original entry on oeis.org

1, 1, 3, 9, 30, 102, 352, 1240, 4443, 16112, 58900, 216727, 801880, 2982327, 11147622, 41854916, 157805863, 597307573, 2268487476, 8639848112, 32999949539, 126498330700, 485441076004, 1865211479514, 7176111235446, 27644828367182, 106633724636570
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 19 2015

Keywords

Comments

a(n) = A103284(2*n,n).

Crossrefs

Programs

  • Haskell
    a257641 n = a103284 (2 * n) n

A103287 Main diagonal of triangle A103286, in which row n+1 is formed by sorting, in ascending order, the result of the convolution of row n with {2,1}.

Original entry on oeis.org

1, 2, 5, 12, 30, 77, 202, 540, 1464, 4014, 11101, 30910, 86542, 243416, 687364, 1947736, 5536216, 15779646, 45088304, 129124925, 370550378, 1065368994, 3068348448, 8851297414, 25571726480, 73981434516, 214317561452
Offset: 0

Views

Author

Paul D. Hanna, Jan 28 2005

Keywords

Crossrefs

Programs

  • PARI
    {a(n)=local(A=vector(n+1,i,vector(i)),B);A[1][1]=1; for(k=1,n,B=vector(k+1);B[1]=2*A[k][1];B[k+1]=A[k][k]; for(i=2,k,B[i]=2*A[k][i]+A[k][i-1]); A[k+1]=vecsort(B));return(A[n+1][n+1])}

Formula

a(n) ~ 3^n*log_3(n)/(18n) (conjecture).
Showing 1-3 of 3 results.