A108783 - OEIS

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A108783

Positions of 1's in A083952, where A083952 gives the integer coefficients a(n) of A(x), where a(n) = 1 or 2 for all n, such that A(x)^(1/2) has only integer coefficients.

0, 2, 6, 10, 12, 26, 30, 32, 36, 50, 52, 56, 60, 62, 126, 130, 132, 136, 150, 152, 160, 164, 166, 170, 172, 174, 176, 180, 184, 192, 194, 198, 200, 202, 214, 216, 220, 226, 228, 230, 234, 236, 240, 242, 244, 260, 262, 264, 272, 274, 278, 282, 286

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Robert G. Wilson v, Table of n, a(n) for n = 1..1356

MATHEMATICA

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]]; Union@ Table[ If[ a[n] == 1, n, 0], {n, 0, 300}] (* Robert G. Wilson v, Nov 25 2006 *)

CROSSREFS

Cf. A083952, A108337, A108338. See A111363 for another version.

Sequence in context: A214963 A140776 A277238 * A235989 A066679 A086123

Adjacent sequences: A108780 A108781 A108782 * A108784 A108785 A108786

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, following a suggestion from Paul D. Hanna, Jun 30 2005

STATUS

approved