login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A343066 Side c of integer-sided primitive triangles (a, b, c) whose angle B = 2*C. 5
4, 9, 16, 25, 36, 49, 9, 64, 81, 100, 121, 25, 144, 169, 196, 225, 49, 16, 256, 289, 324, 25, 361, 81, 400, 441, 484, 529, 121, 576, 49, 625, 676, 729, 25, 169, 64, 784, 841, 900, 961, 225, 1024, 1089, 100, 1156, 1225, 49, 289, 1296, 121, 1369, 1444, 1521, 361, 1600, 1681, 36, 1764, 169, 1849, 81, 441, 1936, 2025, 196 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The triples (a, b, c) are displayed in increasing order of side a, and if sides a coincide then in increasing order of the side b.

This sequence is not increasing because a(7) = 9 < a(6) = 49.

If in triangle ABC, B = 2*C, then the corresponding metric relation between sides is a*c + c^2 = c * (a + c) = b^2.

All terms are perfect squares >= 4.

For the corresponding primitive triples and miscellaneous properties and references, see A343063.

LINKS

Table of n, a(n) for n=1..66.

APMEP, Baccalauréat Mathématiques, Lyon, Septembre 1937.

FORMULA

a(n) = A343063(n, 3)

EXAMPLE

According to inequalities between a, b, c, there exist 3 types of such triangles:

c = 4 with c < a < b for the first triple (5, 6, 4).

c = 9 with c < b < a for the seventh triple (16, 15, 9).

c = 16 with a < c < b for the third triple (9, 20, 16).

MAPLE

for a from 2 to 100 do

for c from 3 to floor(a^2/2) do

d := c*(a+c);

if issqr(d) and igcd(a, sqrt(d), c)=1 and abs(a-c)<sqrt(d) and sqrt(d)<a+c then print(c); end if;

end do;

end do;

CROSSREFS

Cf. A335896 (similar for A < B < C in arithmetic progression).

Cf. A343063 (triples), A343064 (side a), A343065 (side b), A343067 (perimeter).

Sequence in context: A302053 A162496 A159852 * A028907 A292677 A292678

Adjacent sequences:  A343063 A343064 A343065 * A343067 A343068 A343069

KEYWORD

nonn

AUTHOR

Bernard Schott, Apr 12 2021

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 14:12 EDT 2021. Contains 347617 sequences. (Running on oeis4.)