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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A208447 Sum of the k-th powers of the numbers of standard Young tableaux over all partitions of n; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 2, 4, 5, 1, 1, 2, 6, 10, 7, 1, 1, 2, 10, 24, 26, 11, 1, 1, 2, 18, 64, 120, 76, 15, 1, 1, 2, 34, 180, 596, 720, 232, 22, 1, 1, 2, 66, 520, 3060, 8056, 5040, 764, 30, 1, 1, 2, 130, 1524, 16076, 101160, 130432, 40320, 2620, 42
Offset: 0

Views

Author

Alois P. Heinz, Feb 26 2012

Keywords

Examples

			A(3,2) = 1^2 + 2^2 + 1^2 = 6 = 3! because 3 has partitions 111, 21, 3 with 1, 2, 1 standard Young tableaux, respectively:
  .111.    . 21 . . . . . . .    . 3 . . . .
  +---+    +------+  +------+    +---------+
  | 1 |    | 1  2 |  | 1  3 |    | 1  2  3 |
  | 2 |    | 3 .--+  | 2 .--+    +---------+
  | 3 |    +---+     +---+
  +---+
Square array A(n,k) begins:
   1,  1,   1,    1,      1,       1,        1, ...
   1,  1,   1,    1,      1,       1,        1, ...
   2,  2,   2,    2,      2,       2,        2, ...
   3,  4,   6,   10,     18,      34,       66, ...
   5, 10,  24,   64,    180,     520,     1524, ...
   7, 26, 120,  596,   3060,   16076,    86100, ...
  11, 76, 720, 8056, 101160, 1379176, 19902600, ...
		

Crossrefs

Rows 0+1, 2, 3 give: A000012, A007395, A052548.
Main diagonal gives A319607.

Programs

  • Maple
    h:= proc(l) local n; n:=nops(l); add(i, i=l)! /mul(mul(1+l[i]-j
           +add(`if`(l[k]>=j, 1, 0), k=i+1..n), j=1..l[i]), i=1..n)
        end:
    g:= proc(n, i, k, l) `if`(n=0, h(l)^k, `if`(i<1, 0, g(n, i-1, k, l)
           + `if`(i>n, 0, g(n-i, i, k, [l[], i]))))
        end:
    A:= (n, k)-> `if`(n=0, 1, g(n, n, k, [])):
    seq(seq(A(n, d-n), n=0..d), d=0..10);
  • Mathematica
    h[l_] := With[{n = Length[l]}, Sum[i, {i, l}]! / Product[Product[1 + l[[i]] - j + Sum [If[l[[k]] >= j, 1, 0], { k, i+1, n}], {j, 1, l[[i]]}], {i, 1, n}]]; g[n_, i_, k_, l_] := If[n == 0, h[l]^k, If[i < 1, 0, g[n, i-1, k, l] + If[i > n, 0, g[n-i, i, k, Append[l, i]]]]]; a [n_, k_] := If[n == 0, 1, g[n, n, k, {}]]; Table[Table[a[n, d-n], {n, 0, d}], {d, 0, 10}] // Flatten (* Jean-François Alcover, Dec 11 2013, translated from Maple *)

A376033 Number A(n,k) of binary words of length n avoiding distance (i+1) between "1" digits if the i-th bit is set in the binary representation of k; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 2, 1, 2, 4, 1, 2, 3, 8, 1, 2, 4, 5, 16, 1, 2, 3, 6, 8, 32, 1, 2, 4, 4, 9, 13, 64, 1, 2, 3, 8, 6, 15, 21, 128, 1, 2, 4, 5, 12, 9, 25, 34, 256, 1, 2, 3, 6, 7, 18, 13, 40, 55, 512, 1, 2, 4, 4, 8, 11, 27, 19, 64, 89, 1024, 1, 2, 3, 8, 5, 11, 16, 45, 28, 104, 144, 2048
Offset: 0

Views

Author

Alois P. Heinz, Sep 09 2024

Keywords

Comments

Also the number of subsets of [n] avoiding distance (i+1) between elements if the i-th bit is set in the binary representation of k. A(6,3) = 13: {}, {1}, {2}, {3}, {4}, {5}, {6}, {1,4}, {1,5}, {1,6}, {2,5}, {2,6}, {3,6}.
Each column sequence satisfies a linear recurrence with constant coefficients.
The sequence of row n is periodic with period A011782(n) = ceiling(2^(n-1)).

Examples

			A(6,6) = 17: 000000, 000001, 000010, 000011, 000100, 000110, 001000, 001100, 010000, 010001, 011000, 100000, 100001, 100010, 100011, 110000, 110001 because 6 = 110_2 and no two "1" digits have distance 2 or 3.
A(6,7) = 10: 000000, 000001, 000010, 000100, 001000, 010000, 010001, 100000, 100001, 100010.
A(7,7) = 14: 0000000, 0000001, 0000010, 0000100, 0001000, 0010000, 0010001, 0100000, 0100001, 0100010, 1000000, 1000001, 1000010, 1000100.
Square array A(n,k) begins:
     1,  1,   1,  1,   1,  1,  1,  1,   1,  1, ...
     2,  2,   2,  2,   2,  2,  2,  2,   2,  2, ...
     4,  3,   4,  3,   4,  3,  4,  3,   4,  3, ...
     8,  5,   6,  4,   8,  5,  6,  4,   8,  5, ...
    16,  8,   9,  6,  12,  7,  8,  5,  16,  8, ...
    32, 13,  15,  9,  18, 11, 11,  7,  24, 11, ...
    64, 21,  25, 13,  27, 16, 17, 10,  36, 17, ...
   128, 34,  40, 19,  45, 25, 27, 14,  54, 25, ...
   256, 55,  64, 28,  75, 37, 41, 19,  81, 37, ...
   512, 89, 104, 41, 125, 57, 60, 26, 135, 57, ...
		

Crossrefs

Columns k=0-20 give: A000079, A000045(n+2), A006498(n+2), A000930(n+2), A006500, A130137, A079972(n+3), A003269(n+4), A031923(n+1), A263710(n+1), A224809(n+4), A317669(n+4), A351873, A351874, A121832(n+4), A003520(n+4), A208742, A374737, A375977, A375980, A375978.
Rows n=0-2 give: A000012, A007395(k+1), A010702(k+1).
Main diagonal gives A376091.
A(n,2^k-1) gives A141539.
A(2^n-1,2^n-1) gives A376697.
A(n,2^k) gives A209435.

Programs

  • Maple
    h:= proc(n) option remember; `if`(n=0, 1, 2^(1+ilog2(n))) end:
    b:= proc(n, k, t) option remember; `if`(n=0, 1, add(`if`(j=1 and
          Bits[And](t, k)>0, 0, b(n-1, k, irem(2*t+j, h(k)))), j=0..1))
        end:
    A:= (n, k)-> b(n, k, 0):
    seq(seq(A(n, d-n), n=0..d), d=0..12);
  • PARI
    step(v,b)={vector(#v, i, my(j=(i-1)>>1); if(bittest(i-1,0), if(bitand(b,j)==0, v[1+j], 0), v[1+j] + v[1+#v/2+j]));}
    col(n,k)={my(v=vector(2^(1+logint(k,2))), r=vector(1+n)); v[1]=r[1]=1; for(i=1, n, v=step(v,k); r[1+i]=vecsum(v)); r}
    A(n,k)=if(k==0, 2^n, col(n,k)[n+1]) \\ Andrew Howroyd, Oct 03 2024

Formula

A(n,k) = A(n,k+ceiling(2^(n-1))).
A(n,ceiling(2^(n-1))-1) = n+1.
A(n,ceiling(2^(n-2))) = ceiling(3*2^(n-2)) = A098011(n+2).

A309858 Number A(n,k) of k-uniform hypergraphs on n unlabeled nodes; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

2, 1, 2, 1, 2, 2, 1, 1, 3, 2, 1, 1, 2, 4, 2, 1, 1, 1, 4, 5, 2, 1, 1, 1, 2, 11, 6, 2, 1, 1, 1, 1, 5, 34, 7, 2, 1, 1, 1, 1, 2, 34, 156, 8, 2, 1, 1, 1, 1, 1, 6, 2136, 1044, 9, 2, 1, 1, 1, 1, 1, 2, 156, 7013320, 12346, 10, 2, 1, 1, 1, 1, 1, 1, 7, 7013320, 1788782616656, 274668, 11, 2
Offset: 0

Views

Author

Alois P. Heinz, Aug 20 2019

Keywords

Comments

See A000088 and A000665 for more references.

Examples

			Square array A(n,k) begins:
  2, 1,    1,       1,       1,    1, 1, 1, ...
  2, 2,    1,       1,       1,    1, 1, 1, ...
  2, 3,    2,       1,       1,    1, 1, 1, ...
  2, 4,    4,       2,       1,    1, 1, 1, ...
  2, 5,   11,       5,       2,    1, 1, 1, ...
  2, 6,   34,      34,       6,    2, 1, 1, ...
  2, 7,  156,    2136,     156,    7, 2, 1, ...
  2, 8, 1044, 7013320, 7013320, 1044, 8, 2, ...
		

Crossrefs

Cf. A301922, A309865 (the same as triangle).

Programs

  • Maple
    g:= (l, i, n)-> `if`(i=0, `if`(n=0, [[]], []), [seq(map(x->
         [x[], j], g(l, i-1, n-j))[], j=0..min(l[i], n))]):
    h:= (p, v)-> (q-> add((s-> add(`if`(andmap(i-> irem(k[i], p[i]
         /igcd(t, p[i]))=0, [$1..q]), mul((m-> binomial(m, k[i]*m
         /p[i]))(igcd(t, p[i])), i=1..q), 0), t=1..s)/s)(ilcm(seq(
        `if`(k[i]=0, 1, p[i]), i=1..q))), k=g(p, q, v)))(nops(p)):
    b:= (n, i, l, v)-> `if`(n=0 or i=1, 2^((p-> h(p, v))([l[], 1$n]))
         /n!, add(b(n-i*j, i-1, [l[], i$j], v)/j!/i^j, j=0..n/i)):
    A:= proc(n, k) option remember; `if`(k>n, 1,
         `if`(k>n-k, A(n, n-k), b(n$2, [], k)))
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..12);
  • PARI
    permcount(v)={my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
    rep(typ)={my(L=List(), k=0); for(i=1, #typ, k+=typ[i]; listput(L, k); while(#L0, u=vecsort(apply(f, u)); d=lex(u, v)); !d}
    Q(n, k, perm)={my(t=0); forsubset([n, k], v, t += can(Vec(v), t->perm[t])); t}
    T(n, k)={my(s=0); forpart(p=n, s += permcount(p)*2^Q(n, k, rep(p))); s/n!} \\ Andrew Howroyd, Aug 22 2019

Formula

A(n,k) = A(n,n-k) for 0 <= k <= n.
A(n,k) - A(n-1,k) = A301922(n,k) for n,k >= 1.

A216624 Square array read by antidiagonals, T(n,k) = sum_{c|n,d|k} gcd(c,d) for n>=1, k>=1.

Original entry on oeis.org

1, 2, 2, 2, 5, 2, 3, 4, 4, 3, 2, 8, 6, 8, 2, 4, 4, 6, 6, 4, 4, 2, 10, 4, 15, 4, 10, 2, 4, 4, 12, 6, 6, 12, 4, 4, 3, 11, 4, 16, 8, 16, 4, 11, 3, 4, 6, 8, 6, 8, 8, 6, 8, 6, 4, 2, 10, 10, 22, 4, 30, 4, 22, 10, 10, 2, 6, 4, 8, 9, 8, 8, 8, 8, 9, 8, 4, 6
Offset: 1

Views

Author

Peter Luschny, Sep 12 2012

Keywords

Comments

T(n,k) = number of subgroups of C_n X C_k. [Hampjes et al.] - N. J. A. Sloane, Feb 02 2013

Examples

			[----1---2---3---4---5---6---7---8---9--10--11--12]
[ 1] 1,  2,  2,  3,  2,  4,  2,  4,  3,  4,  2,  6
[ 2] 2,  5,  4,  8,  4, 10,  4, 11,  6, 10,  4, 16
[ 3] 2,  4,  6,  6,  4, 12,  4,  8, 10,  8,  4, 18
[ 4] 3,  8,  6, 15,  6, 16,  6, 22,  9, 16,  6, 30
[ 5] 2,  4,  4,  6,  8,  8,  4,  8,  6, 16,  4, 12
[ 6] 4, 10, 12, 16,  8, 30,  8, 22, 20, 20,  8, 48
[ 7] 2,  4,  4,  6,  4,  8, 10,  8,  6,  8,  4, 12
[ 8] 4, 11,  8, 22,  8, 22,  8, 37, 12, 22,  8, 44
[ 9] 3,  6, 10,  9,  6, 20,  6, 12, 23, 12,  6, 30
[10] 4, 10,  8, 16, 16, 20,  8, 22, 12, 40,  8, 32
[11] 2,  4,  4,  6,  4,  8,  4,  8,  6,  8, 14, 12
[12] 6, 16, 18, 30, 12, 48, 12, 44, 30, 32, 12, 90
.
Displayed as a triangular array:
1,
2,  2,
2,  5,  2,
3,  4,  4,  3,
2,  8,  6,  8, 2,
4,  4,  6,  6, 4,  4,
2, 10,  4, 15, 4, 10, 2,
4,  4, 12,  6, 6, 12, 4,  4,
3, 11,  4, 16, 8, 16, 4, 11, 3,
		

Crossrefs

Programs

  • Maple
    with(numtheory):
    T:= (n, k)-> add(add(igcd(c,d), c=divisors(n)), d=divisors(k)):
    seq(seq(T(n, 1+d-n), n=1..d), d=1..14); # Alois P. Heinz, Sep 12 2012
    T:=proc(m,n) local d; add( d*tau(m*n/d^2), d in divisors(gcd(m,n))); end; # N. J. A. Sloane, Feb 02 2013
  • Mathematica
    t[n_, k_] := Sum[Sum[GCD[c, d], {c, Divisors[n]}], {d, Divisors[k]}]; Table[t[n-k+1, k], {n, 1, 12}, {k, 1, n}] // Flatten (* Jean-François Alcover, May 21 2013 *)
  • Sage
    def A216624(n, k) :
        cp = cartesian_product([divisors(n), divisors(k)])
        return reduce(lambda x,y: x+y, map(gcd, cp))
    for n in (1..12): [A216624(n,k) for k in (1..12)]

Formula

T(n,n) = A060724(n) = sum_{d|n} d*tau((n/d)^2).
T(n,1) = T(1,n) = A000005(n) = tau(n).
T(n,2) = T(2,n) = A060710(n) = sum_{d|n} (3-[d is odd]) (Iverson bracket).
T(n+1,n) = A092517(n) = tau(n+1)*tau(n).
T(prime(n),1) = A007395(n) = 2.
T(prime(n),prime(n)) = A113935(n) = prime(n)+3.

A069403 a(n) = 2*Fibonacci(2*n+1) - 1.

Original entry on oeis.org

1, 3, 9, 25, 67, 177, 465, 1219, 3193, 8361, 21891, 57313, 150049, 392835, 1028457, 2692537, 7049155, 18454929, 48315633, 126491971, 331160281, 866988873, 2269806339, 5942430145, 15557484097, 40730022147, 106632582345, 279167724889, 730870592323, 1913444052081
Offset: 0

Views

Author

R. H. Hardin, Mar 22 2002

Keywords

Comments

Half the number of n X 3 binary arrays with a path of adjacent 1's and a path of adjacent 0's from top row to bottom row.
Indices of A017245 = 9*n + 7 = 7, 16, 25, 34, for submitted A153819 = 16, 34, 88,. A153819(n) = 9*a(n) + 7 = 18*F(2*n+1) -2; F(n) = Fibonacci = A000045, 2's = A007395. Other recurrence: a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3). - Paul Curtz, Jan 02 2009

Crossrefs

Cf. 1 X n A000225, 2 X n A016269, vertical path of 1 A069361-A069395, vertical paths of 0+1 A069396-A069416, vertical path of 1 not 0 A069417-A069428, no vertical paths A069429-A069447, no horizontal or vertical paths A069448-A069452.
Equals A052995 - 1.
Bisection of A001595, A062114, A066983.

Programs

  • GAP
    List([0..30], n-> 2*Fibonacci(2*n+1)-1); # G. C. Greubel, Jul 11 2019
  • Magma
    [2*Fibonacci(2*n+1)-1: n in [0..30]]; // Vincenzo Librandi, Apr 18 2011
    
  • Mathematica
    a[n_]:= a[n] = 3a[n-1] - 3a[n-3] + a[n-4]; a[0] = 1; a[1] = 3; a[2] = 9; a[3] = 25; Table[ a[n], {n, 0, 30}]
    Table[2*Fibonacci[2*n+1]-1, {n,0,30}] (* G. C. Greubel, Apr 22 2018 *)
    LinearRecurrence[{4,-4,1},{1,3,9},30] (* Harvey P. Dale, Sep 22 2020 *)
  • PARI
    a(n) = 2*fibonacci(2*n+1)-1 \\ Charles R Greathouse IV, Jun 11 2015
    
  • PARI
    Vec((1-x+x^2)/((1-x)*(1-3*x+x^2)) + O(x^30)) \\ Colin Barker, Nov 02 2016
    
  • Sage
    [2*fibonacci(2*n+1)-1 for n in (0..30)] # G. C. Greubel, Jul 11 2019
    

Formula

a(0) = 1, a(1) = 3, a(2) = 9, a(3) = 25; a(n) = 3*a(n-1) - 3*a(n-3) + a(n-4).
a(n) = 3*a(n-1) - a(n-2) + 1 for n>1, a(1) = 3, a(0) = 0. - Reinhard Zumkeller, May 02 2006
From R. J. Mathar, Feb 23 2009: (Start)
a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3).
G.f.: (1-x+x^2)/((1-x)*(1-3*x+x^2)). (End)
a(n) = 1 + 2*Sum_{k=0..n} Fibonacci(2*k) = 1+2*A027941(n). - Gary Detlefs, Dec 07 2010
a(n) = (2^(-n)*(-5*2^n -(3-sqrt(5))^n*(-5+sqrt(5)) +(3+sqrt(5))^n*(5+sqrt(5))))/5. - Colin Barker, Nov 02 2016

Extensions

Simpler definition from Vladeta Jovovic, Mar 19 2003

A309010 Square array A(n, k) = Sum_{j=0..n} binomial(n,j)^k, n >= 0, k >= 0, read by antidiagonals.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 4, 4, 1, 2, 6, 8, 5, 1, 2, 10, 20, 16, 6, 1, 2, 18, 56, 70, 32, 7, 1, 2, 34, 164, 346, 252, 64, 8, 1, 2, 66, 488, 1810, 2252, 924, 128, 9, 1, 2, 130, 1460, 9826, 21252, 15184, 3432, 256, 10, 1, 2, 258, 4376, 54850, 206252, 263844, 104960, 12870, 512, 11
Offset: 0

Views

Author

Seiichi Manyama, Jul 06 2019

Keywords

Comments

A(n,k) is the constant term in the expansion of (Product_{j=1..k-1} (1 + x_j) + Product_{j=1..k-1} (1 + 1/x_j))^n for k > 0. - Seiichi Manyama, Oct 27 2019
Let B_k be the binomial poset containing all k-tuples of equinumerous subsets of {1,2,...} ordered by inclusion componentwise (described in Stanley reference below). Then A(k,n) is the number of elements in any n-interval of B_k. - Geoffrey Critzer, Apr 16 2020
Column k is the diagonal of the rational function 1 / (Product_{j=1..k} (1-x_j) - Product_{j=1..k} x_j) for k>0. - Seiichi Manyama, Jul 11 2020

Examples

			Square array, A(n, k), begins:
   1,  1,   1,    1,     1,      1, ... A000012;
   2,  2,   2,    2,     2,      2, ... A007395;
   3,  4,   6,   10,    18,     34, ... A052548;
   4,  8,  20,   56,   164,    488, ... A115099;
   5, 16,  70,  346,  1810,   9826, ...
   6, 32, 252, 2252, 21252, 206252, ...
Antidiagonals, T(n, k), begin:
  1;
  1,  2;
  1,  2,   3;
  1,  2,   4,    4;
  1,  2,   6,    8,    5;
  1,  2,  10,   20,   16,     6;
  1,  2,  18,   56,   70,    32,     7;
  1,  2,  34,  164,  346,   252,    64,    8;
  1,  2,  66,  488, 1810,  2252,   924,  128,   9;
  1,  2, 130, 1460, 9826, 21252, 15184, 3432, 256,  10;
		

References

  • R. P. Stanley, Enumerative Combinatorics Vol I, Second Edition, Cambridge, 2011, Example 3.18.3 d, page 366.

Crossrefs

Programs

  • Magma
    [(&+[Binomial(k,j)^(n-k): j in [0..k]]): k in [0..n], n in [0..12]]; // G. C. Greubel, Aug 26 2022
    
  • Mathematica
    nn = 8; Table[ek[x_] := Sum[x^n/n!^k, {n, 0, nn}];Range[0, nn]!^k CoefficientList[Series[ek[x]^2, {x, 0, nn}],x], {k, 0, nn}] // Transpose // Grid (* Geoffrey Critzer, Apr 17 2020 *)
  • PARI
    A(n, k) = sum(j=0, n, binomial(n, j)^k); \\ Seiichi Manyama, Jan 08 2022
    
  • SageMath
    flatten([[sum(binomial(k,j)^(n-k) for j in (0..k)) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Aug 26 2022

Formula

A(n, k) = Sum_{j=0..n} binomial(n,j)^k (array).
A(n, n+1) = A328812(n).
A(n, n) = A167010(n).
T(n, k) = A(k, n-k) (antidiagonals).
T(n, n) = A000027(n+1).
T(n, n-1) = A000079(n-1).
T(n, n-2) = A000984(n-2).
T(n, n-3) = A000172(n-3).
T(n, n-4) = A005260(n-4).
T(n, n-5) = A005261(n-5).
T(n, n-6) = A069865(n-6).
T(n, n-7) = A182421(n-7).
T(n, n-8) = A182422(n-8).
T(n, n-9) = A182446(n-9).
T(n, n-10) = A182447(n-10).
T(n, n-11) = A342294(n-11).
T(n, n-12) = A342295(n-12).
Sum_{n>=0} A(n,k) x^n/(n!^k) = (Sum_{n>=0} x^n/(n!^k))^2. - Geoffrey Critzer, Apr 17 2020

A353486 Primorial base exp-function reduced modulo 4.

Original entry on oeis.org

1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2
Offset: 0

Views

Author

Antti Karttunen, Apr 24 2022

Keywords

Comments

There are no zeros because A276086 is a permutation of A048103.

Crossrefs

Programs

  • PARI
    A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
    A353486(n) = (A276086(n)%4);

Formula

a(n) = A010873(A276086(n)).
For n >= 1, a(n) = A010873(A353516(n) * A353526(n)).
For all n >= 0, a(2n) = A353487(n), a(2n+1) = 2.

A213999 Denominators of the triangle of fractions read by rows: pf(n,0) = 1, pf(n,n) = 1/(n+1) and pf(n+1,k) = pf(n,k) + pf(n,k-1) with 0 < k < n; denominators: A213998.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 6, 4, 1, 2, 3, 12, 5, 1, 2, 6, 12, 60, 6, 1, 2, 3, 4, 10, 20, 7, 1, 2, 6, 12, 20, 20, 140, 8, 1, 2, 3, 12, 15, 10, 35, 280, 9, 1, 2, 6, 4, 20, 30, 70, 280, 2520, 10, 1, 2, 3, 12, 10, 12, 21, 56, 252, 2520, 11, 1, 2, 6, 12, 60, 60, 84, 168, 504, 2520, 27720, 12
Offset: 0

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Author

Reinhard Zumkeller, Jul 03 2012

Keywords

Comments

T(n,0) = 1;
T(n,1) = A007395(n) for n > 0;
T(n,2) = A010704(n) for n > 1;
T(n,n-3) = A124838(n-2) for n > 2;
T(n,n-2) = A027611(n-1) for n > 1;
T(n,n-1) = A002805(n) for n > 0;
T(n,n) = n + 1;
A003418(n+1) = least common multiple of n-th row;
A214075(n,k) = floor(A213998(n,k) / T(n,k)).

Examples

			See A213998.
		

Programs

  • Haskell
    import Data.Ratio ((%), denominator, Ratio)
    a213999 n k = a213999_tabl !! n !! k
    a213999_row n = a213999_tabl !! n
    a213999_tabl = map (map denominator) $ iterate pf [1] where
       pf row = zipWith (+) ([0] ++ row) (row ++ [-1 % (x * (x + 1))])
                where x = denominator $ last row
  • Mathematica
    T[, 0] = 1; T[n, n_] := 1/(n + 1);
    T[n_, k_] := T[n, k] = T[n - 1, k] + T[n - 1, k - 1];
    Table[T[n, k] // Denominator, {n, 0, 11}, {k, 0, n}] // Flatten (* Jean-François Alcover, Nov 10 2021 *)

A245049 Number A(n,k) of hybrid k-ary trees with n internal nodes; square array A(n,k), n>=0, k>=1, read by antidiagonals.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 7, 5, 1, 2, 11, 31, 8, 1, 2, 15, 81, 154, 13, 1, 2, 19, 155, 684, 820, 21, 1, 2, 23, 253, 1854, 6257, 4575, 34, 1, 2, 27, 375, 3920, 24124, 60325, 26398, 55, 1, 2, 31, 521, 7138, 66221, 331575, 603641, 156233, 89, 1, 2, 35, 691, 11764, 148348, 1183077, 4736345, 6210059, 943174, 144
Offset: 0

Views

Author

Alois P. Heinz, Jul 10 2014

Keywords

Examples

			Square array A(n,k) begins:
   1,    1,     1,      1,       1,       1,       1, ...
   2,    2,     2,      2,       2,       2,       2, ...
   3,    7,    11,     15,      19,      23,      27, ...
   5,   31,    81,    155,     253,     375,     521, ...
   8,  154,   684,   1854,    3920,    7138,   11764, ...
  13,  820,  6257,  24124,   66221,  148348,  290305, ...
  21, 4575, 60325, 331575, 1183077, 3262975, 7585749, ...
		

Crossrefs

Rows n=0-2 give: A000012, A007395, A004767(k-1).
Main diagonal gives A245054.

Programs

  • Maple
    A:= (n, k)-> add(binomial((k-1)*n+i, i)*
        binomial((k-1)*n+i+1, n-i), i=0..n)/((k-1)*n+1):
    seq(seq(A(n, 1+d-n), n=0..d), d=0..12);
  • Mathematica
    A[n_, k_] := Sum[Binomial[(k-1)*n+i, i]*Binomial[(k-1)*n+i+1, n-i], {i, 0, n}]/((k-1)*n+1); Table[A[n, 1+d-n], {d, 0, 12}, {n, 0, d}] // Flatten (* Jean-François Alcover, Feb 18 2017, translated from Maple *)

Formula

A(n,k) = 1/((k-1)*n+1) * Sum_{i=0..n} C((k-1)*n+i,i)*C((k-1)*n+i+1,n-i).
A(n,k) = [x^n] ((1+x)/(1-x-x^2))^((k-1)*n+1) / ((k-1)*n+1).
G.f. for column k satisfies: A_k(x) = (1+x*A_k(x)^(k-1)) * (1+x*A_k(x)^k).

A254858 Iterated partial sums of prime numbers, square array read by diagonals.

Original entry on oeis.org

2, 2, 3, 2, 5, 5, 2, 7, 10, 7, 2, 9, 17, 17, 11, 2, 11, 26, 34, 28, 13, 2, 13, 37, 60, 62, 41, 17, 2, 15, 50, 97, 122, 103, 58, 19, 2, 17, 65, 147, 219, 225, 161, 77, 23, 2, 19, 82, 212, 366, 444, 386, 238, 100, 29, 2, 21, 101, 294, 578, 810, 830, 624, 338, 129, 31
Offset: 0

Views

Author

Reinhard Zumkeller, Feb 08 2015

Keywords

Comments

Row n+1 = partial sums of row n.
T(n,1) = A002522(n+1); T(n,2) = A144396(n+1); T(n,3) = A002522(n+2).

Examples

			. n\k | 1  2  3   4   5    6    7     8     9    10    11     12     13
. ----+------------------------------------------------------------------
.  0  | 2  3  5   7  11   13   17    19    23    29    31     37     41 ..
.  1  | 2  5 10  17  28   41   58    77   100   129   160    197    238 ..
.  2  | 2  7 17  34  62  103  161   238   338   467   627    824   1062 ..
.  3  | 2  9 26  60 122  225  386   624   962  1429  2056   2880   3942 ..
.  4  | 2 11 37  97 219  444  830  1454  2416  3845  5901   8781  12723 ..
.  5  | 2 13 50 147 366  810 1640  3094  5510  9355 15256  24037  36760 ..
.  6  | 2 15 65 212 578 1388 3028  6122 11632 20987 36243  60280  97040 ..
.  7  | 2 17 82 294 872 2260 5288 11410 23042 44029 80272 140552 237592 ...
		

Crossrefs

Cf. A000040 (row 0), A007504 (row 1), A014148 (row 2), A014150 (row 3), A178138 (row 4), A254784 (row 5).
Cf. A007395 (column 1), A144396 (column 2), A002522 (column 3).
Cf. A125180 (antidiagonal sums), A125179 (diagonals downward).

Programs

  • Haskell
    a254858_tabl = diags [] $ iterate (scanl1 (+)) a000040_list where
       diags uss (vs:vss) = (map head wss) : diags (map tail wss) vss
                            where wss = vs : uss
    a254858_list = concat a254858_tabl
  • Mathematica
    nmax = 11;
    row[0] = Prime[Range[nmax+1]];
    row[n_] := row[n] = row[n-1] // Accumulate;
    T[n_, k_] := row[n][[k]];
    Table[T[n-k, k], {n, 0, nmax}, {k, 1, n}] // Flatten (* Jean-François Alcover, Oct 11 2021 *)
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