login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A227079 Solutions n to the Diophantine equation: n = (2*x^2 - 1)^2 = (6*y^2 - 5). 1
1, 49, 289, 5041, 274266721 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

x = {1, 2, 3, 6, 91} = A180445(n).

y = {1, 3, 7, 29, 6761} = A227077(n).

(sqrt(2*sqrt(n) + 2) - 1)^2 is a Ramanujan-Nagell Square = {1, 9, 25, 121, 32761} = A227078(n).

REFERENCES

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 181, p. 56, Ellipses, Paris 2008.

L. J. Mordell, Diophantine Equations, Academic Press, NY, 1969, p. 205.

LINKS

Table of n, a(n) for n=0..4.

Richard K. Guy, The Strong Law of Small Numbers (example #29).

Eric Weisstein's World of Mathematics, Ramanujan's Square Equation

CROSSREFS

Cf. A060728, A180445, A227077, A227078.

Sequence in context: A089552 A017354 A239607 * A251222 A250967 A245033

Adjacent sequences:  A227076 A227077 A227078 * A227080 A227081 A227082

KEYWORD

nonn,fini,full

AUTHOR

Raphie Frank, Aug 08 2013

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 December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)