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 A218654 Number of ways to write n as x+y with 0
 0, 1, 1, 1, 2, 1, 2, 2, 2, 1, 4, 1, 4, 2, 4, 2, 3, 2, 6, 3, 4, 3, 6, 2, 6, 3, 4, 3, 8, 3, 8, 2, 5, 5, 8, 4, 8, 6, 5, 4, 8, 2, 10, 6, 6, 3, 11, 4, 9, 6, 9, 7, 10, 4, 14, 6, 9, 3, 11, 4, 12, 7, 9, 10, 10, 4, 11, 5, 10, 9, 15, 4, 15, 9, 9, 8, 14, 6, 12, 8, 9, 8, 18, 4, 17, 11, 9, 11, 20, 5, 14, 10, 13, 7, 16, 9, 17, 6, 16, 10 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Conjecture: a(n)>0 for all n=2,3,4,... It is known that any prime p = 1 or -1 (mod 5) can be written uniquely in the form x(p)^2+3x(p)y(p)+y(p)^2 with x(p)>y(p)>0. Zhi-Wei Sun also conjectured that    (sum_{p

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Last modified March 29 21:32 EDT 2020. Contains 333117 sequences. (Running on oeis4.)