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.

A120111 Bi-diagonal inverse matrix of A120108.

Original entry on oeis.org

1, -2, 1, 0, -3, 1, 0, 0, -2, 1, 0, 0, 0, -5, 1, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, 0, -7, 1, 0, 0, 0, 0, 0, 0, -2, 1, 0, 0, 0, 0, 0, 0, 0, -3, 1, 0, 0, 0, 0, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, -11, 1
Offset: 0

Views

Author

Paul Barry, Jun 09 2006

Keywords

Comments

Subdiagonal is -lcm(1,...,n+2)/lcm(1,...,n+1) or -A014963(n+1).
Row sums are A120112.

Examples

			Triangle begins
   1;
  -2,  1;
   0, -3,  1;
   0,  0, -2,  1;
   0,  0,  0, -5,  1;
   0,  0,  0,  0, -1,  1;
   0,  0,  0,  0,  0, -7,  1;
   0,  0,  0,  0,  0,  0, -2,  1;
   0,  0,  0,  0,  0,  0,  0, -3,  1;
   0,  0,  0,  0,  0,  0,  0,  0, -1,   1;
   0,  0,  0,  0,  0,  0,  0,  0,  0, -11, 1;
		

Crossrefs

Programs

  • Magma
    A014963:= func< n | Lcm([1..n])/Lcm([1..n-1]) >;
    A120111:= func< n,k | k eq n select 1 else k eq n-1 select -A014963(n+1) else 0 >;
    [A120111(n,k): k in [0..n], n in [0..15]]; // G. C. Greubel, May 05 2023
    
  • Mathematica
    T[n_, k_] := Switch[k, n, 1, n-1, -Exp[MangoldtLambda[n+1]], _, 0];
    Table[T[n, k], {n,0,15}, {k,0,n}]//Flatten (* Jean-François Alcover, Mar 01 2021 *)
    (* Second program *)
    A014963[n_]:= LCM@@Range[n]/(LCM@@Range[n-1]);
    A120111[n_, k_]:= If[k==n, 1, If[k==n-1, -A014963[n+1], 0]];
    Table[A120111[n,k], {n,0,20}, {k,0,n}]//Flatten (* G. C. Greubel, May 05 2023 *)
  • SageMath
    def A014963(n): return lcm(range(1,n+1))/lcm(range(1,n))
    def A120111(n,k):
        if (kA014963(n+1)
        else: return 1
    flatten([[A120111(n,k) for k in range(n+1)] for n in range(16)]) # G. C. Greubel, May 05 2023

A120109 Row sums of number triangle A120108.

Original entry on oeis.org

1, 3, 10, 21, 106, 107, 750, 1501, 4504, 4505, 49556, 49557, 644242, 644243, 644244, 1288489, 21904314, 21904315, 416181986, 416181987, 416181988, 416181989, 9572185748, 9572185749, 47860928746, 47860928747, 143582786242
Offset: 0

Views

Author

Paul Barry, Jun 09 2006

Keywords

Comments

It appears that the indices k such that a(k) = a(k-1) + 1 are A080765. - Michel Marcus, Mar 04 2019

Crossrefs

Programs

  • GAP
    List([0..30],n->Sum([0..n],k->Lcm(List([1..n+1],i->i))/Lcm(List([1..k+1],i->i)))); # Muniru A Asiru, Mar 03 2019
    
  • Magma
    A120108:= func< n,k | Lcm([1..n+1])/Lcm([1..k+1]) >;
    [(&+[A120108(n,k): k in [0..n]]): n in [0..50]]; // G. C. Greubel, May 04 2023
    
  • Mathematica
    A120108[n_, k_]:= LCM@@Range[n+1]/(LCM@@Range[k+1]);
    A120109[n_]:= Sum[A120108[n, k], {k,0,n}];
    Table[A120109[n], {n,0,50}] (* G. C. Greubel, May 04 2023 *)
  • PARI
    a(n) = lcm([1..n+1])*sum(k=0, n, 1/lcm([1..k+1])); \\ Michel Marcus, Mar 04 2019
    
  • SageMath
    def f(n): return lcm(range(1,n+2))
    def A120109(n):
        return sum(f(n)//f(k) for k in range(n+1))
    [A120109(n) for n in range(51)] # G. C. Greubel, May 04 2023

Formula

a(n) = Sum_{k=0..n} lcm(1,...,n+1)/lcm(1,...,k+1).

A120110 Diagonal sums of number triangle A120108.

Original entry on oeis.org

1, 2, 7, 15, 67, 92, 461, 1065, 3016, 3956, 29478, 42231, 379107, 547556, 603421, 991923, 12709228, 18540622, 241033695, 352271227, 389226278, 407797820, 5532937710, 8097345425, 30368363481, 41503874738, 98701094676, 127342427241
Offset: 0

Views

Author

Paul Barry, Jun 09 2006

Keywords

Crossrefs

Programs

  • GAP
    List([0..30],n->Sum([0..Int(n/2)],k->Lcm(List([1..n-k+1],i->i))/Lcm(List([1..k+1],i->i)))); # Muniru A Asiru, Mar 04 2019
    
  • Magma
    A120108:= func< n,k | Lcm([1..n+1])/Lcm([1..k+1]) >;
    [(&+[A120108(n-k,k): k in [0..Floor(n/2)]]): n in [0..50]]; // G. C. Greubel, May 04 2023
    
  • Mathematica
    A120108[n_, k_]:= LCM@@Range[n+1]/(LCM@@Range[k+1]);
    A120110[n_]:= Sum[A120108[n-k,k], {k,0,n/2}];
    Table[A120110[n], {n,0,50}] (* G. C. Greubel, May 04 2023 *)
  • PARI
    a(n) = sum(k=0, n\2, lcm([1..n-k+1])/lcm([1..k+1])); \\ Michel Marcus, Mar 04 2019
    
  • SageMath
    def f(n): return lcm(range(1,n+2))
    def A120110(n):
        return sum(f(n-k)//f(k) for k in range((n//2)+1))
    [A120110(n) for n in range(51)] # G. C. Greubel, May 04 2023

Formula

a(n) = Sum_{k=0..floor(n/2)} lcm(1,..,n-k+1)/lcm(1,..,k+1).
Showing 1-3 of 3 results.