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 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), 276-288 (see p. 283). LINKS 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

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Last modified March 22 17:25 EDT 2019. Contains 321422 sequences. (Running on oeis4.)