OFFSET
1,2
COMMENTS
The numbers not of the form 2x^2+3y^2+3z^2.
Also values of n such that numbers of the form x^2+n*y^2 for some integers x, y cannot have prime factor of 3 raised to an odd power. - V. Raman, Dec 18 2013
Numbers whose squarefree part is congruent to 1 modulo 3. - Peter Munn, May 17 2020
LINKS
L. J. Mordell, A new Waring's problem with squares of linear forms, Quart. J. Math., 1 (1930), 276-288 (see p. 283).
FORMULA
a(n) = 8n/3 + O(log n). - Charles R Greathouse IV, Dec 19 2013
a(n) = A055041(n)/3. - Peter Munn, May 17 2020
PROG
(PARI) is(n)=n/=9^valuation(n, 9); n%3==1 \\ Charles R Greathouse IV and V. Raman, Dec 19 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 01 2000
STATUS
approved