A188982 Even numbers x such that x^2 + y^2 = 13^n with x and y coprime.

0, 2, 12, 46, 120, 122, 828, 6554, 28560, 86158, 145668, 246046, 3369960, 17021162, 58317492, 128629846, 13651680, 1590277918, 9719139348, 37641223154, 99498527400, 107655263398, 647549275812, 5284814079046, 23290743888720, 71041880304722, 123471611274972, 182714776311554, 2701419604443960, 13833225534613558, 47880898349909868

Offset

0,2

Comments

The y values are in A188983.

This is also the absolute value of the imaginary part of (3+2i)^n, where i = sqrt(-1).

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..183

Mathematica

Table[s = Select[PowersRepresentations[13^n, 2, 2], CoprimeQ @@ # &, 1][[1]]; Select[s, EvenQ][[1]], {n, 0, 30}]

Prog

(Magma) [Integers()!Abs(Im((3+2*Sqrt(-1))^n)): n in [0..30]]; // Bruno Berselli, May 26 2011

Crossrefs

Cf. A158936, A188983.

Sequence in context: A066258 A123771 A046991 * A061990 A006742 A003993

Adjacent sequences: A188979 A188980 A188981 * A188983 A188984 A188985

Keyword

nonn

Author

T. D. Noe, Apr 14 2011

Status

approved