A146945 - OEIS

A146945

Hypotenuses of primitive Pythagorean triples which are not prime numbers and which are the hypotenuse of a unique triangle.

25, 125, 169, 289, 625, 841, 1369, 1681, 2197, 2809, 3125, 3721, 4913, 5329, 7921, 9409, 10201, 11881, 12769, 15625, 18769, 22201, 24389, 24649, 28561, 29929, 32761, 37249, 38809, 50653, 52441, 54289, 58081, 66049, 68921, 72361, 76729, 78125

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

OFFSET

1,1

COMMENTS

Each term is a prime power of the form p^e where p is in A002144 and e>1.

A proper subset of A120960 by eliminating A002144.

A proper subset of A120961 by eliminating A024409.

A proper subset of A008846 by eliminating A002144 and A024409.

A proper subset of A020882 by eliminating A002144, A024409 and duplicate entries.

LINKS

Ray Chandler, Table of n, a(n) for n = 1..10000

MATHEMATICA

lst1 = {1, 1}; lst2 = {}; Do[ If[ GCD[m, n] == 1, a = 2m*n; b = m^2 - n^2; c = m^2 + n^2; If[ !PrimeQ@c, AppendTo[lst1, c]]], {m, 3, 1000}, {n, If[OddQ@m, 2, 1], m - 1, 2}]; lst1 = Sort@ lst1; Do[ If[ lst1[[n - 1]] != lst1[[n]] && lst1[[n]] != lst1[[n + 1]], AppendTo[lst2, lst1[[n]]]], {n, 2, Length@ lst1 - 1}]; Take[lst2, 50] (* Robert G. Wilson v, May 02 2009 *)

CROSSREFS

Cf. A020882, A008846, A002144, A024409, A120960, A120961.

Sequence in context: A280390 A225388 A369563 * A044357 A044738 A062672

Adjacent sequences: A146942 A146943 A146944 * A146946 A146947 A146948

KEYWORD

nonn

AUTHOR

John Harrison (harrison_uk_2000(AT)yahoo.co.uk), Apr 20 2009

EXTENSIONS

a(7) corrected by and a(17) and further terms from Robert G. Wilson v, May 02 2009

Minor edits to comments. - Ray Chandler, Nov 27 2019

STATUS

approved