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A135796 Numbers of the form 4x^3y+4y x^3 (where x,y are positive integers). 3
8, 40, 120, 128, 272, 312, 520, 640, 648, 888, 1160, 1200, 1400, 1920, 2040, 2048, 2080, 2952, 2968, 3240, 3280, 4040, 4352, 4872, 4992, 5000, 5368, 6120, 6960, 7008, 7280, 7320, 8320, 8840, 9720 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Squares of these numbers are of the form N^4-M^2 (where N belongs to A135786 and M to A135797) Proof uses: (4x^3y+4xy^3)^2=(x^2-y^2)^4+(x^4+6x^2y^2+y^4)^2.

Refers to A057102, which had an incorrect description and has been replaced by A256418. As a result the present sequence should be re-checked. - N. J. A. Sloane, Apr 06 2015

LINKS

Table of n, a(n) for n=1..35.

MATHEMATICA

a = {}; Do[Do[w = 4x^3y + 4x y^3; If[w < 10000, AppendTo[a, w]], {x, y, 1000}], {y, 1, 1000}]; Union[a] (*Artur Jasinski*)

CROSSREFS

Cf. A000404, A050803, A057102, A135784, A060803, A135786, A135787, A135789, A135790, A135791, A135792, A135793, A135795, A135796, A135797.

Sequence in context: A211631 A279273 A143943 * A105374 A162668 A227733

Adjacent sequences: A135793 A135794 A135795 * A135797 A135798 A135799

KEYWORD

nonn

AUTHOR

Artur Jasinski, Nov 29 2007

STATUS

approved

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Last modified January 31 11:22 EST 2023. Contains 359971 sequences. (Running on oeis4.)