A179784 Records for minima of the positive distance d between the seventh power of a positive integer x and the square of an integer y such that d = x^7 - y^2 (x <> k^2 and y <> k^7).

7, 71, 95, 448, 1756, 2215, 3983, 6271, 15231, 26775, 26870, 57475, 102703, 221916, 257963, 9053750, 9297464, 9321703, 27188154, 48787589, 62396287, 83146412, 152244535, 44475611670, 74378479183, 179884971502, 929051699593

Offset

1,1

Comments

Distance d is equal to 0 when x = k^2 and y = k^7.

For x values see A179785.

For y values see A179786.

Conjecture (Artur Jasinski): For any positive number x >= A179785(n), the distance d between the seventh power of x and the square of any y (such that x <> k^2 and y <> k^7) can't be less than A179784(n).

Links

Table of n, a(n) for n=1..27.

Mathematica

d = 7; max = 1000; vecd = Table[10^100, {n, 1, max}]; vecx = Table[10^100, {n, 1, max}]; vecy = Table[10^100, {n, 1, max}]; len = 1; Do[m = Floor[(n^d)^(1/2)]; k = n^d - m^2; If[k != 0, ile = 0; Do[If[vecd[[z]] < k, ile = ile + 1], {z, 1, len}]; len = ile + 1; vecd[[len]] = k; vecx[[len]] = n; vecy[[len]] = m], {n, 1, 10000000}]; dd = {}; xx = {}; yy = {}; Do[AppendTo[dd, vecd[[n]]]; AppendTo[xx, vecx[[n]]]; AppendTo[yy, vecy[[n]]], {n, 1, len}]; dd

Crossrefs

Cf. A179107, A179108, A179109, A179386, A179387, A179388, A179407, A179408, A179785, A179786.

Sequence in context: A090155 A326740 A107163 * A142037 A087390 A142928

Adjacent sequences: A179781 A179782 A179783 * A179785 A179786 A179787

Keyword

nonn

Author

Artur Jasinski, Jul 27 2010

Status

approved