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A180968 The only integers that cannot be partitioned into a sum of six positive squares. 2
1, 2, 3, 4, 5, 7, 8, 10, 11, 13, 16, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

From R. J. Mathar, Sep 11 2012: (Start)

Not the sum of 7 positive squares: 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 14, 17, 20.

Not the sum of 8 positive squares: 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 15, 18, 21.

Not the sum of 9 positive squares: 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 13, 14, 16, 19, 22.

Not the sum of 10 positive squares: 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 14, 15, 17, 20, 23. (End)

REFERENCES

Dubouis, E.; L'Interm. des math., vol. 18, (1911), pp. 55-56, 224-225.

Grosswald, E.; Representation of Integers as Sums of Squares, Springer-Verlag, New York Inc., (1985), pp.73-74.

LINKS

Table of n, a(n) for n=1..12.

Gordon Pall, On Sums of Squares, The American Mathematical Monthly, Vol. 40, No. 1, (January 1933), pp. 10-18.

FORMULA

Let B be the set of integers {1,2,4,5,7,10,13}. Then, for s>=6, every integer can be partitioned into a sum of s positive squares except for 1,2,...,s-1 and s+b where b is a member of the set B [Dubouis].

EXAMPLE

As the sixth integer which cannot be partitioned into a sum of six positive squares is 7, we have a(6)=7.

MATHEMATICA

s=6; B={1, 2, 4, 5, 7, 10, 13}; Union[Range[s-1], s+B]//Sort

CROSSREFS

Cf. A047701 (not the sum of 5 squares)

Sequence in context: A025199 A213858 A277992 * A191847 A321290 A274337

Adjacent sequences:  A180965 A180966 A180967 * A180969 A180970 A180971

KEYWORD

fini,full,nonn

AUTHOR

Ant King, Sep 30 2010

STATUS

approved

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Last modified February 17 02:22 EST 2020. Contains 331976 sequences. (Running on oeis4.)