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.

A091352 Row sums of triangle A091351, in which the k-th column lists the row sums of the k-th power of A091351 (when considered as a lower triangular matrix).

Original entry on oeis.org

1, 2, 4, 9, 24, 77, 295, 1329, 6934, 41351, 278680, 2101434, 17574552, 161740316, 1626733108, 17771416521, 209739328924, 2661301094008, 36148700652163, 523597247829867, 8059284921781892, 131408547139817541
Offset: 0

Views

Author

Paul D. Hanna, Jan 02 2004

Keywords

Comments

Equals column 1 of table A125781. Equals row sums and column 0 (shifted) of triangle A127420. - Paul D. Hanna, Feb 11 2007

Crossrefs

A127452 Triangle, read by rows of n*(n+1)/2 + 1 terms, generated by the recurrence: start with a single '1' in row 0; row n+1 is generated from row n by first inserting zeros at positions {(m+1)*(m+2)/2 - 1, m>=0} in row n and then taking the partial sums in reverse order.

Original entry on oeis.org

1, 1, 1, 2, 2, 1, 1, 6, 6, 4, 4, 2, 1, 1, 24, 24, 18, 18, 12, 8, 8, 4, 2, 1, 1, 120, 120, 96, 96, 72, 54, 54, 36, 24, 16, 16, 8, 4, 2, 1, 1, 720, 720, 600, 600, 480, 384, 384, 288, 216, 162, 162, 108, 72, 48, 32, 32, 16, 8, 4, 2, 1, 1
Offset: 0

Views

Author

Paul D. Hanna, Jan 15 2007

Keywords

Comments

The first column equals the factorials. Triangle A127420 is generated by a similar recurrence.

Examples

			The triangle begins:
1;
1, 1;
2, 2, 1, 1;
6, 6, 4, 4, 2, 1, 1;
24, 24, 18, 18, 12, 8, 8, 4, 2, 1, 1;
120, 120, 96, 96, 72, 54, 54, 36, 24, 16, 16, 8, 4, 2, 1, 1;
720, 720, 600, 600, 480, 384, 384, 288, 216, 162, 162, 108, 72, 48, 32, 32, 16, 8, 4, 2, 1, 1;
...
The recurrence is illustrated by the following examples.
Start with a single '1' in row 0.
To get row 1, insert 0 in row 0 at position 0,
and take partial sums in reverse order:
0,_1;
1,_1;
To get row 2, insert 0 in row 1 at positions [0,2],
and take partial sums in reverse order:
0,_1,_0,_1;
2,_2,_1,_1;
To get row 3, insert 0 in row 2 at positions [0,2,5],
and take partial sums in reverse order:
0,_2,_0,_2,_1,_0,_1;
6,_6,_4,_4,_2,_1,_1;
To get row 4, insert 0 in row 3 at positions [0,2,5,9],
and take partial sums in reverse order:
_0,__6,__0,__6,__4,_0,_4,_2,_1,_0,_1;
24,_24,_18,_18,_12,_8,_8,_4,_2,_1,_1;
etc.
Continuing in this way generates the factorials in the first column.
		

Crossrefs

Cf. A018927, A127420, A047969, A182961 (variant).

Programs

  • PARI
    T(n,k)=if(n<0 || k<0,0,if(n==0 && k==0,1, if(k==0, n!, if(issquare(8*k+1),T(n,k-1),T(n,k-1)-T(n-1,k-(sqrtint(8*k+1)+1)\2)))))
    
  • PARI
    T(n,k)=local(t=(sqrtint(8*k+1)-1)\2);(n-t)!*(n-t)^(k-t*(t+1)/2)*(n-t+1)^(t-k+t*(t+1)/2)

Formula

Sum_{k=0..n*(n+1)/2} k*T(n,k) = A018927(n+1) = Sum_{k=0..n} k*k!*{(k+1)^(n-k+1)-k^(n-k+1)}.
T(n,k) = (n-t)! * (n-t)^(k - t*(t+1)/2) * (n-t+1)^(t-k + t*(t+1)/2) where t=floor((sqrt(8*k+1)-1)/2). Also, Sum_{j=k*(k+1)/2..(k+1)*(k+2)/2-1} T(n,j) = A047969(n-k,k) = (n-k)!*((n-k+1)^(k+1)-(n-k)^(k+1)).

A127714 Triangle, read by rows of (n+1)*(n+2)/2 terms, generated by the following rule. Start with a single '1' in row n=0; from then on, obtain row n from row n-1 by inserting zeros in row n-1 at positions: {(j+1)*n - j*(j-1)/2 | j=0..n} and then take partial sums.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 2, 3, 3, 3, 1, 3, 5, 5, 8, 11, 11, 14, 14, 14, 1, 4, 9, 14, 14, 22, 33, 44, 44, 58, 72, 72, 86, 86, 86, 1, 5, 14, 28, 42, 42, 64, 97, 141, 185, 185, 243, 315, 387, 387, 473, 559, 559, 645, 645, 645, 1, 6, 20, 48, 90, 132, 132, 196, 293, 434, 619, 804, 804
Offset: 0

Views

Author

Paul D. Hanna, Jan 24 2007

Keywords

Examples

			Triangle begins:
  1;
  1, 1, 1;
  1, 2, 2, 3, 3, 3;
  1, 3, 5, 5, 8, 11, 11, 14, 14, 14;
  1, 4, 9, 14, 14, 22, 33, 44, 44, 58, 72, 72, 86, 86, 86;
  1, 5, 14, 28, 42, 42, 64, 97, 141, 185, 185, 243, 315, 387, 387, 473, 559, 559, 645, 645, 645;
  1, 6, 20, 48, 90, 132, 132, 196, 293, 434, 619, 804, 804, 1047, 1362, 1749, 2136, 2136, 2609, 3168, 3727, 3727, 4372, 5017, 5017, 5662, 5662, 5662;
  ...
Obtain row n from row n-1 by inserting zeros in row n-1 at positions:
[n,2*n,3*n-1,4*n-3,5*n-6,6*n-10,...,(j+1)*n - j*(j-1)/2,... | j=0..n],
and then take partial sums; illustrated by the following examples.
Obtain row 3 from row 2 by inserting zeros at positions [3,6,8,9],
and then take partial sums:
[1, 2, 2, 0, 3, 3, 0, 3, 0, 0];
[1, 3, 5, 5, 8,11,11,14,14,14];
Obtain row 4 from row 3 by inserting zeros at positions [4,8,11,13,14],
and then take partial sums:
[1, 3, 5, _5, _0, _8, 11, 11, _0, 14, 14, _0, 14, _0, _0];
[1, 4, 9, 14, 14, 22, 33, 44, 44, 58, 72, 72, 86, 86, 86].
		

Crossrefs

Programs

  • PARI
    {T(n,k)=local(t);if(n<0 || k<0 || k>(n+1)*(n+2)/2-1,0, t=(sqrtint((2*n+3)^2-8*(k+1))-1)\2; if(k==0,1,if(issquare((2*n+3)^2-8*(k+1)),T(n,k-1),T(n,k-1)+T(n-1,k-n+t))))} {/* for(n=0,8,for(k=0,(n+1)*(n+2)/2-1,print1(T(n,k),","));print("")) */}

Formula

T(n,n) = A000108(n);
A009766 (Catalan's triangle) forms lower left sub-triangle;
T(n+1,2*n+1) = A127632(n), where g.f. of A127632 is: 2/(1+sqrt(2*sqrt(1-4*x)-1)).
T(n,n*(n+1)/2) = A127716(n).
T(n,(n+1)*(n+2)/2-1) = A127715(n).
Showing 1-3 of 3 results.