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Search: id:A083952
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| A083952 |
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Integer coefficients of A(x), where 1<=a(n)<=2, such that A(x)^(1/2) consists entirely of integer coefficients. |
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29
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| 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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More generally, "integer coefficients of A(x), where 1<=a(n)<=m, such that A(x)^(1/m) consists entirely of integer coefficients", appears to have a unique solution for all m. Is this sequence periodic?
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LINKS
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Robert G. Wilson v, Table of n, a(n) for n = 0..5506
N. Heninger, E. M. Rains and N. J. A. Sloane, On the Integrality of n-th Roots of Generating Functions, J. Combinatorial Theory, Series A, 113 (2006), 1732-1745.
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MATHEMATICA
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a[n_] := a[n] = Block[{s = Sum[a[i]*x^i, {i, 0, n - 1}]}, If[ IntegerQ@ Last@ CoefficientList[ Series[ Sqrt[s + x^n], {x, 0, n}], x], 1, 2]]; Table[ a[n], {n, 0, 104}] (* from Robert G. Wilson v (rgwv@rgwv.com), Nov 25 2006 *)
s = 0; a[n_] := a[n] = Block[{}, If[IntegerQ@ Last@ CoefficientList[ Series[ Sqrt[s + x^n], {x, 0, n}], x], s = s + x^n; 1, s = s + 2 x^n; 2]]; Table[ a@n, {n, 0, 104}] (* from Robert G. Wilson v (rgwv@rgwv.com), Sep 08 2007 *)
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CROSSREFS
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Cf. A084202 (A(x)^(1/2)), A108335 (A084202 mod 4), A108336 (A084202 mod 2), A108340 (a(n) mod 2). Positions of 1's: A108783.
Cf. A083953, A083954, A083945, A083946.
Sequence in context: A029428 A101422 A070304 this_sequence A043529 A080942 A099812
Adjacent sequences: A083949 A083950 A083951 this_sequence A083953 A083954 A083955
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KEYWORD
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nonn,nice
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), May 09 2003
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EXTENSIONS
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More terms from njas, Jul 02 2005
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