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 1-7 of 7 results.

A230761 Indices k where the sum over k-th powers of the integers in a k X k square in the Gaussian plane (A230308) is not == 0 (mod k).

Original entry on oeis.org

24, 48, 96, 120, 168, 192, 240, 264, 312, 336, 384, 408, 456, 480, 528, 552, 600, 624, 672, 696, 744, 768, 816, 840, 888, 912, 960, 984, 1008, 1032, 1056, 1104, 1128, 1176, 1200, 1248, 1272, 1320, 1344, 1392, 1416, 1464
Offset: 1

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Author

Jose Maria Grau Ribas, Oct 16 2013

Keywords

Comments

Define S(k) = Sum_{0<=a 0 (mod k).
Almost the same as A073763, but contains also 1008 (equivalent to A230310(1)), for example.
The asymptotic density of this sequence is 0.028999... (Fortuny Ayuso et al., 2014). - Amiram Eldar, May 01 2021

Crossrefs

The complement of A230308.

A230310 Numbers k such that Sum_{a=0..72*k-1, b=0..72*k-1} (a+b*i)^(72*k) !== 0 (mod 72*k), where i is the imaginary unit.

Original entry on oeis.org

14, 28, 42, 55, 56, 70, 84, 95, 110, 112, 126, 140, 154, 165, 168, 182, 190, 210, 220, 224, 238, 252, 266, 275, 280, 285, 308, 322, 330, 336, 350, 364, 378, 380, 385, 406, 420, 434, 440, 448, 462, 475, 476, 495, 504, 506, 518, 532, 546, 550, 560, 570, 574, 602, 616, 630, 644, 658, 660, 665, 672, 700, 714, 715, 728, 742
Offset: 1

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Crossrefs

Programs

  • Mathematica
    aa[n_] := Mod[Sum[PowerMod[ a + b I, n, n], {a, n}, {b, n}], n]; Select[Range[100], aa[72*#] > 0 &]

Extensions

Terms a(7) onward from Max Alekseyev, Oct 16 2013

A230309 Sum_{0<=a<24*n, 0<=b<24*n} (a+b*i)^(24*n) (mod 24*n), where i is the imaginary unit.

Original entry on oeis.org

8, 32, 0, 32, 80, 0, 56, 128, 0, 80, 176, 0, 104, 272, 0, 128, 272, 0, 152, 320, 0, 176, 368, 0, 200, 416, 0, 416, 464, 0, 248, 512, 0, 272, 560, 0, 296, 608, 0, 320, 656, 432, 344, 704, 0, 368, 752, 0, 392, 800, 0, 416, 848, 0, 560, 320, 0, 464, 944, 0, 488
Offset: 1

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Author

Keywords

Comments

If m <> 0 (mod 24) then Sum_{(a+b*i)^m: 0<=a

Crossrefs

Programs

  • Mathematica
    aa[n_] := aa[n] = Mod[Sum[PowerMod[a + b *I, n, n], {a, n}, {b, n}], n]; Table[aa[24*n],{n,1,10}]
  • PARI
    a(n)=my(N=24*n,a);lift(sum(A=0,N-1,a=Mod(A,N);sum(b=0,N-1,(a+b*I)^N))) \\ Charles R Greathouse IV, Nov 05 2013

A232819 Real part of the sum over the n-th powers of all Gaussian integers in the n X n base square in the first quadrant.

Original entry on oeis.org

1, 0, -144, -2568, -28200, 0, 15203328, 675195936, 16696909080, 0, -25789252433472, -1612260342054360, -54804262577596532, 0, 161017938434267136000, 13718166932451951573120, 621130358284578576358416, 0, -3008072527724272784969384000, -320196271193421334219630013080
Offset: 1

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Keywords

Crossrefs

Programs

  • Mathematica
    g[n_] := Sum[(a + b I)^n, {a, 1, n}, {b, 1, n}]; Table[Re[g[n]], {n, 33}]
  • PARI
    vector(100, n, real(sum(x=1, n, sum(y=1, n, (x+I*y)^n)))) \\ Colin Barker, Nov 09 2014

Formula

a(A016825(n)) = 0, for n>=0. - Michel Marcus, Nov 09 2014

A232820 Imaginary part of the sum over the n-th powers of all Gaussian integers in the n X n base square in the first quadrant.

Original entry on oeis.org

1, 18, 144, 0, -28200, -814968, -15203328, 0, 16696909080, 893794451000, 25789252433472, 0, -54804262577596532, -4044941639317807200, -161017938434267136000, 0, 621130358284578576358416, 59512584052525004199214632, 3008072527724272784969384000, 0
Offset: 1

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Crossrefs

Programs

  • Mathematica
    g[n_] := Sum[(a + b I)^n, {a, 1, n}, {b, 1, n}]; Table[Im[g[n]], {n, 33}]
  • PARI
    vector(100, n, imag(sum(x=1, n, sum(y=1, n, (x+I*y)^n)))) \\ Colin Barker, Nov 09 2014

Formula

Conjecture: a(4n) = 0. - Michel Marcus, Nov 09 2014

A232056 Numbers k such that S(24*(3*k+1)) !== 8*(3*k+1) (mod 24*(3*k+1)) where S(j) := Sum_{a=0..j-1, b=0..j-1} (a+b*i)^j and i is the imaginary unit; i.e., A230309(3*k+1) != 8*(3*k+1).

Original entry on oeis.org

9, 18, 23, 37, 51
Offset: 1

Author

Keywords

Comments

In most cases S(24*(3*k+1)) == 8*(3*k+1) (mod 24*(3*k+1)).

Crossrefs

Programs

  • Mathematica
    fu[n_] := fu[n] = Mod[Sum[PowerMod[i + j I, n, n], {i, 0, n - 1}, {j, 0, n - 1}], n]; Select[Range[50], ! fu[24*(3 # +1)] == 8*(3 # +1) &]

A232057 Numbers k such that S(24*(3*k-1)) <> 16*(3*k-1) mod 24*(3*k-1) where S(k) := Sum_{0<=a

Original entry on oeis.org

5, 19, 37, 47, 61, 75
Offset: 1

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Keywords

Crossrefs

Programs

  • Mathematica
    fu[n_] := fu[n] = Mod[Sum[PowerMod[i + j I, n, n], {i, 0, n - 1}, {j, 0, n - 1}], n]; Table[If[! fu[24(3n - 1)]/(3n - 1) == 16, Print[n]; n], {n, 1, 40}]
Showing 1-7 of 7 results.