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

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A105426 a(0)=1, a(1)=5, a(n)=8*a(n-1)-a(n-2). 3
1, 5, 39, 307, 2417, 19029, 149815, 1179491, 9286113, 73109413, 575589191, 4531604115, 35677243729, 280886345717, 2211413522007, 17410421830339, 137071961120705, 1079165267135301, 8496250175961703, 66890836140558323 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

15*a(n)^2-14 is a square for all n.

LINKS

Table of n, a(n) for n=0..19.

Tanya Khovanova, Recursive Sequences

Index entries for linear recurrences with constant coefficients, signature (8,-1).

Index entries for two-way infinite sequences

FORMULA

G.f.: (1-3x)/(1-8x+x^2). a(n)=2*A105045(2*n+1)-1. a(-n)=2*A105045(2*n)-1, if n>0.

a(n)=(1/2)*[4-sqrt(15)]^n-(1/30)*[4-sqrt(15)]^n*sqrt(15)+(1/2)*[4+sqrt(15)]^n+(1/30)*sqrt(15) *[4+sqrt(15)]^n, with n>=0 - Paolo P. Lava, Jul 08 2008

MATHEMATICA

LinearRecurrence[{8, -1}, {1, 5}, 20] (* Harvey P. Dale, Feb 25 2016 *)

PROG

(PARI) a(n)=subst(19*poltchebi(n)-poltchebi(n-1), x, 4)/15

CROSSREFS

Cf. a(n) = A001090(n+1) - 3*A001090(n).

Sequence in context: A221357 A201442 A135849 * A273019 A244039 A213233

Adjacent sequences:  A105423 A105424 A105425 * A105427 A105428 A105429

KEYWORD

nonn,easy

AUTHOR

Michael Somos, Apr 10 2005

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 21 16:27 EST 2017. Contains 295003 sequences.