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!)
A282116 Numbers k such that k-1/2*R(k) and k+1/2*R(k) are both positive squares, where R(k) is the digits reverse of k. 0
468, 4842, 27225, 235890, 21030930, 840827745 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Similar to rare numbers A035519.
No more terms < 10^12. - Lars Blomberg, Jul 12 2017
a(7), if it exists, is larger than 2*10^15. - Giovanni Resta, Jul 14 2017
LINKS
EXAMPLE
(468 - 1/2*864)^(1/2) = (36)^(1/2) = 6 and (468 +1/2*864)^(1/2) = (900)^(1/2) = 30.
MAPLE
R:=proc(w) local x, y, z; x:=w; y:=0; for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10); od; y; end:
P:=proc(q, k) local n; for n from 1 to q do
if n>k*R(n) then if frac(sqrt(n-k*R(n)))=0 and frac(sqrt(n+k*R(n)))=0
then print(n); fi; fi; od; end: P(10^9, 1/2);
CROSSREFS
Sequence in context: A054756 A205415 A205408 * A281061 A270259 A205407
KEYWORD
nonn,base,more
AUTHOR
Paolo P. Lava, Feb 16 2017
EXTENSIONS
a(6) from Lars Blomberg, Jul 12 2017
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 04:13 EDT 2024. Contains 371235 sequences. (Running on oeis4.)