

A047449


Numbers that are primitively represented by x^2+y^2+z^2.


9



1, 2, 3, 5, 6, 9, 10, 11, 13, 14, 17, 18, 19, 21, 22, 25, 26, 27, 29, 30, 33, 34, 35, 37, 38, 41, 42, 43, 45, 46, 49, 50, 51, 53, 54, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 73, 74, 75, 77, 78, 81, 82, 83, 85, 86, 89, 90, 91, 93, 94, 97, 98, 99, 101, 102, 105, 106
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..67.
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,1)


FORMULA

Numbers that are congruent to {1, 2, 3, 5, 6} mod 8.
Union of A047449 and A034045 is A000378. Intersection of A047449 and A034043 is A034046. Numbers that are in A000378 and not congruent to 0 mod 4.  Ray Chandler, Sep 05 2004
G.f. x*(1+x+x^2+2*x^3+x^4+2*x^5) / ( (x^4+x^3+x^2+x+1)*(x1)^2 ).  R. J. Mathar, Dec 07 2011
a(1)=1, a(2)=2, a(3)=3, a(4)=5, a(5)=6, a(6)=9, a(n)=a(n1)+a(n5)a(n6).  Harvey P. Dale, Mar 05 2015


MATHEMATICA

LinearRecurrence[{1, 0, 0, 0, 1, 1}, {1, 2, 3, 5, 6, 9}, 70] (* Harvey P. Dale, Mar 05 2015 *)


PROG

(PARI) a(n)=(n1)\5*8+[6, 1, 2, 3, 5][n%5+1] \\ Charles R Greathouse IV, Jun 11 2015


CROSSREFS

Cf. A000378, A004215, A034043A034047.
Sequence in context: A069880 A230044 A069861 * A162923 A107040 A045989
Adjacent sequences: A047446 A047447 A047448 * A047450 A047451 A047452


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane.


STATUS

approved



