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 1-10 of 26 results. Next

A002635 Number of partitions of n into 4 squares.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 3, 2, 2, 2, 2, 1, 1, 3, 3, 3, 3, 2, 2, 2, 1, 3, 4, 2, 4, 3, 3, 2, 2, 3, 4, 3, 2, 4, 2, 2, 2, 4, 5, 3, 5, 3, 5, 3, 1, 4, 5, 3, 3, 4, 3, 4, 2, 4, 6, 4, 4, 4, 5, 2, 3, 5, 5, 5, 5, 4, 4, 3, 2, 6, 7, 4, 5, 5, 5, 4, 2, 5, 9, 5, 3, 5, 4, 3, 1, 6, 7, 6, 7, 5, 7, 5, 3, 6, 7, 4
Offset: 0

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Author

Keywords

Comments

a(A124978(n)) = n; a(A006431(n)) = 1; a(A180149(n)) = 2; a(A245022(n)) = 3. - Reinhard Zumkeller, Jul 13 2014

Examples

			1: 1000; 2: 1100; 3:1110; 4: 2000 and 1111; 5: 2100; 6: 2110; 7: 2111; 8: 2200; 9: 3000 and 2210; 10: 3100 and 2211; etc.
		

References

  • G. Loria, Sulla scomposizione di un intero nella somma di numeri poligonali. (Italian) Atti Accad. Naz. Lincei. Rend. Cl. Sci. Fis. Mat. Nat. (8) 1, (1946). 7-15.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Equivalent sequences for other numbers of squares: A010052 (1), A000161 (2), A000164 (3), A000174 (5), A000177 (6), A025422 (7), A025423 (8), A025424 (9), A025425 (10).

Programs

  • Haskell
    a002635 = p (tail a000290_list) 4 where
    p ks'@(k:ks) c m = if m == 0 then 1 else
    if c == 0 || m < k then 0 else p ks' (c - 1) (m - k) + p ks c m
    -- Reinhard Zumkeller, Jul 13 2014
  • Mathematica
    Length[PowersRepresentations[ #, 4, 2]] & /@ Range[0, 107] (* Ant King, Oct 19 2010 *)
  • PARI
    for(n=1,100,print1(sum(a=0,n,sum(b=0,a,sum(c=0,b,sum(d=0,c,if(a^2+b^2+c^2+d^2-n,0,1))))),","))
    
  • PARI
    a(n)=local(c=0); if(n>=0, forvec(x=vector(4,k,[0,sqrtint(n)]),c+=norml2(x)==n,1)); c
    

A000174 Number of partitions of n into 5 squares.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 1, 2, 2, 2, 2, 2, 3, 2, 1, 3, 3, 3, 3, 4, 3, 3, 2, 2, 4, 4, 4, 4, 5, 3, 3, 4, 3, 5, 5, 5, 6, 5, 3, 5, 5, 5, 6, 5, 6, 5, 4, 4, 6, 7, 6, 8, 8, 7, 5, 6, 5, 8, 8, 4, 9, 7, 6, 7, 7, 8, 9, 9, 7, 9, 6, 7, 8, 10, 9, 9, 11, 7, 8, 8, 8, 11, 11, 9, 12, 11, 7, 9, 9, 12, 13, 9, 10, 11, 8, 6, 10, 13, 13, 13
Offset: 0

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Author

Keywords

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, NY, 1985, p. 84.

Crossrefs

Equivalent sequences for other numbers of squares: A010052 (1), A000161 (2), A000164 (3), A002635 (4), A000177 (6), A025422 (7), A025423 (8), A025424 (9), A025425 (10).
Cf. A025429, A295160 (largest number k with a(k) = n).

Programs

  • Mathematica
    Table[PowersRepresentations[n, 5, 2] // Length, {n, 0, 100}] (* Jean-François Alcover, Feb 04 2016 *)

A295494 Smallest number with exactly n representations as a sum of six nonnegative squares.

Original entry on oeis.org

0, 4, 9, 17, 20, 30, 29, 38, 36, 45, 52, 53, 54, 65, 74, 68, 83, 77, 90, 84, 86, 99, 100, 107, 101, 108, 110, 117, 129, 116, 131, 125, 126, 146, 152, 140, 134, 192, 156, 149, 161
Offset: 0

Views

Author

Robert Price, Nov 22 2017

Keywords

Comments

It appears that a(n) does not exist for n in {42, 55, 61, 74, 99, 100, 103, 125, 135, 139, 148, 152, 161, 162, 164, 168, 180, 182, 194, 196}; i.e., there is no integer whose number of representations is any of these values.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

Programs

  • Mathematica
    Table[SelectFirst[Range@ 200, Length@ PowersRepresentations[#, 6, 2] == n &] - Boole[n == 1], {n, 41}] (* Michael De Vlieger, Nov 26 2017 *)

A295669 Largest number with exactly n representations as a sum of six nonnegative squares.

Original entry on oeis.org

7, 15, 23, 31, 32, 40, 48, 55, 64, 58, 63, 71, 79, 96, 88, 78, 85, 97, 112, 93, 106, 111, 120, 121, 128, 136, 130, 122, 160, 145, 139, 141, 151, 168, 159, 157, 169, 192, 156, 184, 178
Offset: 1

Views

Author

Robert Price, Nov 25 2017

Keywords

Comments

It appears that a(42) does not exist.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

A295489 Numbers that have exactly six representations as a sum of six nonnegative squares.

Original entry on oeis.org

30, 33, 34, 35, 39, 40
Offset: 1

Views

Author

Robert Price, Nov 22 2017

Keywords

Comments

This sequence is finite and complete. See the von Eitzen Link and the proof in A294675 stating that for n > 5408, the number of ways to write n as a sum of 5 squares (without allowing zero squares) is at least floor(sqrt(n - 101) / 8) = 9. Since this sequence relaxes the restriction of zero squares and allows one more square, the number of representations for n > 5408 is at least nine. Then an inspection of n <= 5408 completes the proof.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

A295670 Numbers that have exactly one representation as a sum of six positive squares.

Original entry on oeis.org

6, 9, 12, 14, 15, 17, 18, 20, 22, 23, 25, 26, 27, 28, 31, 32, 34, 35, 37, 40, 43
Offset: 1

Views

Author

Robert Price, Nov 25 2017

Keywords

Comments

It appears that this sequence is finite and complete. See the von Eitzen link for a proof for the 5 positive squares case.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

Programs

  • Mathematica
    m = 6;
    r[n_] := Reduce[xx = Array[x, m]; 0 <= x[1] && LessEqual @@ xx && AllTrue[xx, Positive] && n == Total[xx^2], xx, Integers];
    For[n = 0, n < 50, n++, rn = r[n]; If[rn[[0]] === And, Print[n, " ", rn]]] (* Jean-François Alcover, Feb 25 2019 *)
    b[n_, i_, k_, t_] := b[n, i, k, t] = If[n == 0, If[t == 0, 1, 0], If[i<1 || t<1, 0, b[n, i - 1, k, t] + If[i^2 > n, 0, b[n - i^2, i, k, t - 1]]]];
    T[n_, k_] := b[n, Sqrt[n] // Floor, k, k];
    Position[Table[T[n, 6], {n, 0, 100}], 1] - 1 // Flatten (* Jean-François Alcover, Nov 06 2020, after Alois P. Heinz in A243148 *)

Formula

A243148(a(n),6) = 1. - Alois P. Heinz, Feb 25 2019

A295702 Largest number with exactly n representations as a sum of six positive squares.

Original entry on oeis.org

43, 64, 67, 82, 91, 106, 112, 109, 115, 133, 139, 154, 131, 160, 146, 178, 163, 181, 166, 169, 202, 187, 172, 226, 208, 211, 229, 196, 217, 232, 203, 256, 223, 274, 253
Offset: 1

Views

Author

Robert Price, Nov 25 2017

Keywords

Comments

It appears that a(36) does not exist.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

A295485 Numbers that have exactly two representations as a sum of six nonnegative squares.

Original entry on oeis.org

4, 5, 6, 8, 10, 11, 15
Offset: 1

Views

Author

Robert Price, Nov 22 2017

Keywords

Comments

This sequence is finite and complete. See the von Eitzen Link and the proof in A294675 stating that for n > 5408, the number of ways to write n as a sum of 5 squares (without allowing zero squares) is at least floor(sqrt(n - 101) / 8) = 9. Since this sequence relaxes the restriction of zero squares and allows one more square, the number of representations for n > 5408 is at least nine. Then an inspection of n <= 5408 completes the proof.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

A295486 Numbers that have exactly three representations as a sum of six nonnegative squares.

Original entry on oeis.org

9, 12, 13, 14, 16, 19, 23
Offset: 1

Views

Author

Robert Price, Nov 22 2017

Keywords

Comments

This sequence is finite and complete. See the von Eitzen Link and the proof in A294675 stating that for n > 5408, the number of ways to write n as a sum of 5 squares (without allowing zero squares) is at least floor(sqrt(n - 101) / 8) = 9. Since this sequence relaxes the restriction of zero squares and allows one more square, the number of representations for n > 5408 is at least nine. Then an inspection of n <= 5408 completes the proof.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

A295487 Numbers that have exactly four representations as a sum of six nonnegative squares.

Original entry on oeis.org

17, 18, 22, 24, 31
Offset: 1

Views

Author

Robert Price, Nov 22 2017

Keywords

Comments

This sequence is finite and complete. See the von Eitzen Link and the proof in A294675 stating that for n > 5408, the number of ways to write n as a sum of 5 squares (without allowing zero squares) is at least floor(sqrt(n - 101) / 8) = 9. Since this sequence relaxes the restriction of zero squares and allows one more square, the number of representations for n > 5408 is at least nine. Then an inspection of n <= 5408 completes the proof.

References

  • E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, New York, 1985, p. 86, Theorem 1.

Crossrefs

Showing 1-10 of 26 results. Next