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A261915 Smallest x such that n can be written as n = x^2 + y^2 + z^2 with x >= y >= z >= 0, or -1 if no such x exists. 4
0, 1, 1, 1, 2, 2, 2, -1, 2, 2, 3, 3, 2, 3, 3, -1, 4, 3, 3, 3, 4, 4, 3, -1, 4, 4, 4, 3, -1, 4, 5, -1, 4, 4, 4, 5, 4, 6, 5, -1, 6, 4, 5, 5, 6, 5, 6, -1, 4, 6, 5, 5, 6, 6, 5, -1, 6, 5, 7, 5, -1, 6, 6, -1, 8, 6, 5, 7, 6, 7, 6, -1, 6, 6, 7, 5, 6, 6, 7, -1, 8, 6, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

a(n) = -1 iff n is in A004215, a(n) >= 0 iff n is in A000378.

If we maximize x we get A261904.

LINKS

David Consiglio, Jr., Table of n, a(n) for n = 0..10000

David Consiglio, Jr., Python Program

Index entries for sequences related to sums of squares

EXAMPLE

Table showing initial values of n,x,y,z:

   0  0  0  0

   1  1  0  0

   2  1  1  0

   3  1  1  1

   4  2  0  0

   5  2  1  0

   6  2  1  1

   7 -1 -1 -1

   8  2  2  0

   9  2  2  1

  10  3  1  0

  11  3  1  1

  12  2  2  2

  13  3  2  0

  14  3  2  1

  15 -1 -1 -1

  16  4  0  0

  17  3  2  2

  18  3  3  0

  19  3  3  1

  20  4  2  0

  ...

CROSSREFS

Cf. A000378, A004215, A005875, A261904.

Analogs for 4 squares: A178786 and A122921.

Sequence in context: A083338 A241900 A204018 * A109037 A147680 A192895

Adjacent sequences:  A261912 A261913 A261914 * A261916 A261917 A261918

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Sep 11 2015

EXTENSIONS

a(17) corrected, more terms from David Consiglio, Jr., Sep 11 2015

STATUS

approved

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Last modified August 22 07:40 EDT 2019. Contains 326172 sequences. (Running on oeis4.)