A101904 Number of leg-hypotenuse twin Pythagorean triples < 10^n.

1, 6, 21, 70, 223, 706, 2235, 7070, 22360, 70710, 223606, 707106, 2236067, 7071067, 22360679, 70710677, 223606797, 707106780, 2236067976, 7071067811, 22360679774, 70710678118, 223606797749, 707106781186, 2236067977499

Offset

1,2

Links

Table of n, a(n) for n=1..25.

Eric Weisstein's World of Mathematics, Twin Pythagorean Triple

Example

For a(2)=6 because {3, 4, 5}, {5, 12, 13}, {7, 24, 25}, {9, 40, 41}, {11, 60, 61}, {13, 84, 85}.

Mathematica

f[n_] := Round[ Sqrt[ (10^n - 1)/2] - 1]; Table[ f[n], {n, 25}] (* Robert G. Wilson v, Jan 08 2005 *)

Crossrefs

Cf. A095861, length of the longer leg in A046092, length of hypotenuse in A001844.

Sequence in context: A200761 A169687 A302448 * A022814 A000390 A000391

Adjacent sequences: A101901 A101902 A101903 * A101905 A101906 A101907

Keyword

nonn

Author

Eric W. Weisstein, Dec 20 2004

Status

approved