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!)
A099942 Start with 1, then alternately double or add 2. 1
1, 2, 4, 8, 10, 20, 22, 44, 46, 92, 94, 188, 190, 380, 382, 764, 766, 1532, 1534, 3068, 3070, 6140, 6142, 12284, 12286, 24572, 24574, 49148, 49150, 98300, 98302, 196604, 196606, 393212, 393214, 786428, 786430, 1572860, 1572862, 3145724, 3145726 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..5000

Index entries for linear recurrences with constant coefficients, signature (0,3,0,-2).

FORMULA

a(0)=1; for n > 0, a(n) = a(n-1)*(1 + n mod 2) + 2*((n+1) mod 2).

G.f.: (2*x^3 + x^2 + 2*x + 1)/(2*x^4 - 3*x^2 + 1).

3*2^ceiling(n/2) + (-1)^n - 3. - Ralf Stephan, Dec 04 2004

a(2*n) = A033484(n).

a(n-1) + a(n) = A061776(n) for n > 0.

E.g.f.: -2*cosh(x) + 3*cosh(sqrt(2)*x) - 4*sinh(x) + 3*sqrt(2)*sinh(sqrt(2)*x). - Franck Maminirina Ramaharo, Nov 08 2018

MATHEMATICA

LinearRecurrence[{0, 3, 0, -2}, {1, 2, 4, 8}, 50] (* Harvey P. Dale, May 03 2016 *)

PROG

(PARI) print1(a=1, ", "); for(n=1, 20, print1(a=2*a, ", ", a=a+2, ", "))

(MAGMA) [3*2^Ceiling(n/2) + (-1)^n - 3: n in [0..50]]; // Vincenzo Librandi, Aug 17 2011

CROSSREFS

Cf. A033484, A061776, A075427, A083416.

Sequence in context: A287266 A306719 A185400 * A033092 A177909 A259386

Adjacent sequences:  A099939 A099940 A099941 * A099943 A099944 A099945

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 12 2004

EXTENSIONS

Edited and extended by Klaus Brockhaus, Nov 13 2004

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 00:30 EST 2019. Contains 329988 sequences. (Running on oeis4.)