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 A072401 1 iff n is of the form 4^m*(8k+7). 10
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 OFFSET 0,1 COMMENTS Characteristic function of A004215, indicating numbers not the sum of 3 integer squares. LINKS J.-P. Allouche and J. Shallit, The ring of k-regular sequences, Theoretical Computer Sci., 98 (1992), 163-197; preprint. See Example 20. Eric Weisstein's World of Mathematics, Square Numbers. FORMULA a(n) = 1 - A057427(7 - A072400(n)). CROSSREFS a(A004215(k)) = 1 for k>0, a(n) = A057427(A064873(n)), for k<112: a(n)=A064873(n), but A064873(112)=2, as also a(112 - 1) = 1. Cf. A071374. Sequence in context: A187946 A323510 A044938 * A064873 A295659 A188436 Adjacent sequences:  A072398 A072399 A072400 * A072402 A072403 A072404 KEYWORD nonn AUTHOR Reinhard Zumkeller, Jun 16 2002 STATUS approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)