|
Search: id:A146984
|
|
|
| A146984 |
|
The numbers are the integer-valued contraharmonic means of two positive integers u and v (u < v) and ordered by increasing u and increasing v (u = 2, 3, 4, ...; v = u+1, u+2, ...). |
|
+0
1
|
|
| 5, 5, 13, 10, 25, 17, 41, 10, 15, 26, 61, 37, 85, 20, 50, 113, 15, 39, 65, 145, 13, 25, 34, 82, 181, 101, 221, 17, 20, 30, 52, 75, 122, 265, 145, 313, 29, 35, 74, 170, 365, 25, 29, 51, 65, 123, 197, 421
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Any number a(n) is also a hypotenuse number A009003 (and conversely).
|
|
LINKS
|
Contraharmonic proportion
|
|
FORMULA
|
The contraharmonic mean of u and v is (u^2+v^2)/(u+v).
|
|
EXAMPLE
|
a(1) = (2^2+6^2)/(2+6) = 5, a(2) = (3^2+6^2)/(3+6) = 5, a(3) = (3^2+15^2)/(3+15) = 10
|
|
PROGRAM
|
(Other) K = 50, L = 2222 FOR u = 2 TO K FOR v = u TO L a := (u^2+v^2)/(u+v) IF INT(a) = a THEN PRINT u, v, a NEXT v NEXT u
|
|
CROSSREFS
|
Sequence in context: A122213 A049735 A055526 this_sequence A055524 A132981 A147280
Adjacent sequences: A146981 A146982 A146983 this_sequence A146985 A146986 A146987
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Pahikkala Jussi (pahio(AT)wakkanet.fi), Nov 04 2008
|
|
|
Search completed in 1.331 seconds
|
