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.

A215200 Triangle read by rows, Kronecker symbol (n-k|k) for n >= 1, 1 <= k <= n.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, -1, -1, 1, 0, 1, 0, 0, 0, 1, 0, 1, -1, 1, 1, -1, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, -1, 0, 1, 0, 1, 1, -1, 1, 1, 1, 1, -1, 1, 1, 0, 1, 0, 0, 0, -1, 0, -1, 0, 0, 0, 1, 0
Offset: 1

Views

Author

Peter Luschny, Aug 05 2012

Keywords

Comments

Signed version of A054521.

Examples

			Triangle begins:
  1,
  1,  0,
  1,  1,  0,
  1,  0,  1, 0,
  1, -1, -1, 1,  0,
  1,  0,  0, 0,  1, 0,
  1, -1,  1, 1, -1, 1,  0,
  1,  0, -1, 0, -1, 0,  1, 0,
  1,  1,  0, 1,  1, 0,  1, 1, 0,
  1,  0,  1, 0,  0, 0, -1, 0, 1, 0,
From _Jianing Song_, Dec 26 2018: (Start)
This sequence can also be arranged into a square array T(n,k) = Kronecker symbol(n|k) with n >= 0, k >= 1, read by antidiagonals:
  1  0  0  0  0  0  0 ... ((0|k) = A000007(k+1))
  1  1  1  1  1  1  1 ... ((1|k) = A000012)
  1  0 -1  0 -1  0 -1 ... ((2|k) = A091337)
  1 -1  0  1 -1  0 -1 ... ((3|k) = A091338)
  1  0  1  0  1  0  1 ... ((4|k) = A000035)
  1 -1 -1  1  0  1 -1 ... ((5|k) = A080891)
  1  0  0  0  1  0 -1 ... ((6|k) = A322796)
  1  1  1  1 -1  1  0 ... ((7|k) = A089509)
  ... (End)
		

References

  • Henri Cohen: A Course in Computational Algebraic Number Theory, p. 29.

Crossrefs

Rows of square array include: A000012, A091337, A091338, A000035, A080891, A322796, A089509.

Programs

  • Magma
    /* As triangle */ [[KroneckerSymbol(n-k, k):  k in [1..n]]: n in [1..21]]; // Vincenzo Librandi, Apr 24 2018
  • Maple
    A215200_row := n -> seq(numtheory[jacobi](n-k,k),k=1..n);
    for n from 1 to 13 do A215200_row(n) od;
  • Mathematica
    Column[Table[KroneckerSymbol[n - k, k], {n, 10}, {k, n}], Center] (* Alonso del Arte, Aug 06 2012 *)
  • PARI
    T(n,k) = kronecker(n-k, k);
    tabl(nn) = for(n=1, nn, for(k=1, n, print1(T(n,k), ", ")); print); \\ Michel Marcus, Apr 24 2018
    
  • Sage
    def A215200_row(n): return [kronecker_symbol(n-k,k) for k in (1..n)]
    for n in (1..13): print(A215200_row(n))
    

A215284 Numbers m such that Sum_{k=1..m} (m - k | k) = 0, where (i|j) is the Kronecker symbol.

Original entry on oeis.org

5, 8, 12, 18, 20, 21, 24, 28, 32, 40, 44, 48, 52, 53, 56, 60, 68, 69, 72, 76, 77, 80, 84, 88, 92, 96, 99, 104, 108, 112, 116, 120, 124, 125, 126, 128, 132, 136, 140, 141, 148, 150, 152, 156, 160, 162, 164, 165, 168, 172, 176, 180, 184, 188, 189, 192, 197
Offset: 1

Views

Author

Peter Luschny, Aug 07 2012

Keywords

Comments

Appears to include all multiples of 4 that are not squares. - Robert Israel, Mar 11 2018

Crossrefs

Programs

  • Maple
    f:= n -> add(numtheory:-jacobi(n-k,k),k=1..n):
    select(n -> f(n)=0, [$1..300]); # Robert Israel, Mar 11 2018
  • Mathematica
    Select[ Range[200], Sum[ KroneckerSymbol[# - k, k], {k, 1, #}] == 0 & ] (* Jean-François Alcover, Jul 29 2013 *)
  • PARI
    is(m) = sum(k = 1, m, kronecker(m-k, k)) == 0; \\ Amiram Eldar, Nov 07 2024
  • Sage
    def A215200_row(n): return [kronecker_symbol(n-k, k) for k in (1..n)]
    [n for n in (1..197) if sum(A215200_row(n)) == 0]
    

A215285 Numbers m such that Sum_{k=1..m} (m - k | k) = phi(m), where (i|j) is the Kronecker symbol and phi(m) is the Euler totient function.

Original entry on oeis.org

1, 2, 3, 4, 6, 9, 16, 36, 64, 100, 144, 196, 256, 324, 400, 484, 576, 676, 784, 900, 1024, 1156, 1296, 1444, 1600, 1764, 1936, 2116, 2304, 2500, 2704, 2916, 3136, 3364, 3600, 3844, 4096, 4356, 4624, 4900, 5184, 5476, 5776, 6084, 6400, 6724, 7056, 7396, 7744
Offset: 1

Views

Author

Peter Luschny, Aug 07 2012

Keywords

Comments

n is in this sequence if and only if sum_{k=1..n} (n-k|k) = sum_{k=1..n} |(n-k|k)|.

Crossrefs

Programs

  • Mathematica
    Reap[ Do[ If[ Sum[ KroneckerSymbol[n - k, k], {k, 1, n}] == EulerPhi[n], Print[n]; Sow[n]], {n, 1, 8000}]][[2, 1]] (* Jean-François Alcover, Jul 29 2013 *)
  • PARI
    is(m) = sum(k = 1, m, kronecker(m-k, k)) == eulerphi(m); \\ Amiram Eldar, Nov 08 2024
  • Sage
    def A215200_row(n): return [kronecker_symbol(n-k, k) for k in (1..n)]
    [n for n in (1..1000) if sum(A215200_row(n)) == euler_phi(n)]
    
Showing 1-3 of 3 results.