

A055047


Numbers of the form 9^i*(3*j+1).


6



1, 4, 7, 9, 10, 13, 16, 19, 22, 25, 28, 31, 34, 36, 37, 40, 43, 46, 49, 52, 55, 58, 61, 63, 64, 67, 70, 73, 76, 79, 81, 82, 85, 88, 90, 91, 94, 97, 100, 103, 106, 109, 112, 115, 117, 118, 121, 124, 127, 130, 133, 136, 139, 142, 144, 145, 148, 151
(list;
graph;
refs;
listen;
history;
text;
internal format)



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


REFERENCES

L. J. Mordell, A new Waring's problem with squares of linear forms, Quart. J. Math., 1 (1930), 276288 (see p. 283).


LINKS

Table of n, a(n) for n=1..58.


FORMULA

a(n) = 8n/3 + O(log n).  Charles R Greathouse IV, Dec 19 2013


PROG

(PARI) is(n)=n/=9^valuation(n, 9); n%3==1 \\ Charles R Greathouse IV and V. Raman, Dec 19 2013


CROSSREFS

Cf. A055046, A055048, A233998, A233999.
Sequence in context: A010389 A010415 A010442 * A234429 A291201 A310940
Adjacent sequences: A055044 A055045 A055046 * A055048 A055049 A055050


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Jun 01 2000


STATUS

approved



