login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A309395 Number of integer-sided triangles with sides a,b,c, max(a,b) < c, a + c = n that are right triangles. 1
0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 1, 2, 0, 1, 0, 0, 0, 0, 3, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 3, 4, 0, 0, 0, 2, 0, 1, 0, 0, 0, 0, 0, 0, 1, 3, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 2, 0, 0, 0, 0, 1, 4, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 3, 0, 6, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,18
LINKS
FORMULA
a(n) > 0 if and only if n is a term in A046790.
a(n^2) = floor((n-1)/2) = A004526(n-1).
EXAMPLE
n | (a,b,c)
-----+-----------------------------------------
8 | [ 3, 4, 5]
9 | [ 4, 3, 5]
16 | [ 6, 8, 10]
18 | [ 5, 12, 13], [ 8, 6, 10]
24 | [ 9, 12, 15]
25 | [ 8, 15, 17], [12, 5, 13]
27 | [12, 9, 15]
32 | [ 7, 24, 25], [12, 16, 20], [15, 8, 17]
36 | [10, 24, 26], [16, 12, 20]
PROG
(PARI) {a(n) = sum(k=n\2+1, n-1, issquare(k^2-(n-k)^2))}
CROSSREFS
Sequence in context: A117371 A117370 A332007 * A260943 A316893 A316897
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 28 2019
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)