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!)
A092270 If n mod 2 == 0 then 3^n else 2^n. 0
1, 2, 9, 8, 81, 32, 729, 128, 6561, 512, 59049, 2048, 531441, 8192, 4782969, 32768, 43046721, 131072, 387420489, 524288, 3486784401, 2097152, 31381059609, 8388608, 282429536481, 33554432, 2541865828329, 134217728, 22876792454961, 536870912, 205891132094649 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
The convergent series 1/2 + 1/9 + 1/8 + 1/81 + 1/32 + ... fails the ratio test.
REFERENCES
B. R. Gelbaum and J. M. H. Olmsted, Counterexamples in Analysis, Holden-Day, San Francisco, 1964; see p. 60.
LINKS
FORMULA
From R. J. Mathar, Apr 28 2008: (Start)
O.g.f.: -(-1+4x^2-2x+18x^3)/((3x-1)(3x+1)(2x-1)(2x+1)).
a(n) = 13a(n-2) - 36a(n-4). (End)
From Amiram Eldar, Jul 06 2022: (Start)
Sum_{n>=0} 1/a(n) = 43/24.
Sum_{n>=0} (-1)^n/a(n) = 11/24. (End)
MATHEMATICA
Table[ If[ EvenQ[n], 3^n, 2^n], {n, 0, 30}] (* Robert G. Wilson v, Feb 18 2004 *)
PROG
(PARI) a(n) = if (n%2, 2^n, 3^n); \\ Michel Marcus, Jul 06 2022
CROSSREFS
Sequence in context: A092397 A272348 A351166 * A249225 A191351 A324553
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 16 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 10:22 EDT 2024. Contains 371268 sequences. (Running on oeis4.)