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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A350122 Square array T(n,k), n >= 1, k >= 1, read by antidiagonals downwards, where T(n,k) = Sum_{j=1..n} floor(n/(2*j-1))^k.

Original entry on oeis.org

1, 1, 2, 1, 4, 4, 1, 8, 10, 5, 1, 16, 28, 17, 7, 1, 32, 82, 65, 27, 9, 1, 64, 244, 257, 127, 41, 11, 1, 128, 730, 1025, 627, 225, 55, 12, 1, 256, 2188, 4097, 3127, 1313, 353, 70, 15, 1, 512, 6562, 16385, 15627, 7809, 2419, 522, 93, 17, 1, 1024, 19684, 65537, 78127, 46721, 16841, 4114, 759, 115, 19
Offset: 1

Views

Author

Seiichi Manyama, Dec 16 2021

Keywords

Examples

			Square array begins:
   1,  1,   1,    1,     1,      1,      1, ...
   2,  4,   8,   16,    32,     64,    128, ...
   4, 10,  28,   82,   244,    730,   2188, ...
   5, 17,  65,  257,  1025,   4097,  16385, ...
   7, 27, 127,  627,  3127,  15627,  78127, ...
   9, 41, 225, 1313,  7809,  46721, 280065, ...
  11, 55, 353, 2419, 16841, 117715, 823673, ...
		

Crossrefs

Columns k=1..3 give A060831, A350143, A350144.
T(n,n) gives A350145.
Cf. A344725.

Programs

  • Mathematica
    T[n_, k_] := Sum[Floor[n/(2*j - 1)]^k, {j, 1, n}]; Table[T[k, n - k + 1], {n, 1, 11}, {k, 1, n}] // Flatten (* Amiram Eldar, Dec 17 2021 *)
  • PARI
    T(n, k) = sum(j=1, n, (n\(2*j-1))^k);
    
  • PARI
    T(n, k) = sum(j=1, n, sumdiv(j, d, j/d%2*(d^k-(d-1)^k)));

Formula

G.f. of column k: (1/(1 - x)) * Sum_{j>=1} (j^k - (j - 1)^k) * x^j/(1 - x^(2*j)).
T(n,k) = Sum_{j=1..n} Sum_{d|j, j/d odd} d^k - (d - 1)^k.

A350163 a(n) = Sum_{k=1..n} (-1)^(k+1) * floor(n/(2*k-1))^3.

Original entry on oeis.org

1, 8, 26, 63, 125, 209, 335, 504, 703, 981, 1311, 1671, 2141, 2681, 3269, 3990, 4808, 5643, 6669, 7847, 8963, 10343, 11861, 13349, 15212, 17170, 19078, 21310, 23748, 26172, 28962, 31939, 34759, 38133, 41769, 45190, 49188, 53400, 57396, 62246, 67168, 71704, 77122
Offset: 1

Views

Author

Seiichi Manyama, Dec 18 2021

Keywords

Crossrefs

Column 3 of A350161.

Programs

  • Mathematica
    a[n_] := Sum[(-1)^(k + 1) * Floor[n/(2*k - 1)]^3, {k, 1, n}]; Array[a, 50] (* Amiram Eldar, Dec 18 2021 *)
  • PARI
    a(n) = sum(k=1, n, (-1)^(k+1)*(n\(2*k-1))^3);
    
  • PARI
    a(n) = sum(k=1, n, sumdiv(k, d, kronecker(-4, k/d)*(d^3-(d-1)^3)));
    
  • PARI
    my(N=66, x='x+O('x^N)); Vec(sum(k=1, N, (k^3-(k-1)^3)*x^k/(1+x^(2*k)))/(1-x))

Formula

a(n) = Sum_{k=1..n} Sum_{d|k} A101455(k/d) * (d^3 - (d - 1)^3).
G.f.: (1/(1 - x)) * Sum_{k>=1} (k^3 - (k-1)^3) * x^k/(1 + x^(2*k)).
Showing 1-2 of 2 results.