OFFSET
0,2
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.
LINKS
D. H. Lehmer, On the Partition of Numbers into Squares, The American Mathematical Monthly, Vol. 55, No. 8, October 1948, pp. 476-481.
MATHEMATICA
Table[SelectFirst[Range@ 200, Length@ PowersRepresentations[#, 6, 2] == n &] - Boole[n == 1], {n, 41}] (* Michael De Vlieger, Nov 26 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Price, Nov 22 2017
STATUS
approved