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

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A157843 1728000n - 1343760. 3
384240, 2112240, 3840240, 5568240, 7296240, 9024240, 10752240, 12480240, 14208240, 15936240, 17664240, 19392240, 21120240, 22848240, 24576240, 26304240, 28032240, 29760240, 31488240, 33216240, 34944240, 36672240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (103680000*n^2-161251200*n+62697601)^2-(3600*n^2-5599*n+2177)*(1728000*n-1343760)^2=1 can be written as A157844(n)^2-A157842(n)*a(n)^2=1.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Vincenzo Librandi, X^2-AY^2=1

Index entries for linear recurrences with constant coefficients, signature (2,-1).

FORMULA

a(n) = 2*a(n-1) -a(n-2).

G.f.: x*(384240+1343760*x)/(x-1)^2.

MATHEMATICA

LinearRecurrence[{2, -1}, {384240, 2112240}, 40]

PROG

(MAGMA) I:=[384240, 2112240]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];

(PARI) a(n) = 1728000*n - 1343760.

CROSSREFS

Cf. A157842, A157844.

Sequence in context: A271323 A205759 A205589 * A206167 A206381 A234216

Adjacent sequences:  A157840 A157841 A157842 * A157844 A157845 A157846

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Mar 07 2009

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 2 10:39 EST 2020. Contains 338876 sequences. (Running on oeis4.)