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!)
A093361 Add/multiply sequence, see example. 15
1, 3, 7, 11, 27, 33, 69, 77, 141, 151, 251, 263, 407, 421, 617, 633, 889, 907, 1231, 1251, 1651, 1673, 2157, 2181, 2757, 2783, 3459, 3487, 4271, 4301, 5201, 5233, 6257, 6291, 7447, 7483, 8779, 8817, 10261, 10301, 11901, 11943, 13707, 13751, 15687, 15733, 17849 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
It appears that a(2*n+1) = 2*(n + A002623(2*n-1)) + 3. - Carl Najafi, Jan 21 2013
LINKS
FORMULA
a(n) = (1/24)*(4*n^3 + 12*n^2 + 20*n + 33 + (6*n^2 - 9)*(-1)^n). - Ralf Stephan, Dec 02 2004
G.f.: (1 + 2*x + x^2 - 2*x^3 + 7*x^4 - x^6)/((1 + x)^3*(x - 1)^4). - R. J. Mathar, May 20 2013
E.g.f.: ((12 + 15*x + 15*x^2 + 2*x^3)*cosh(x) + (21 + 21*x + 9*x^2 + 2*x^3)*sinh(x))/12. - Stefano Spezia, Apr 18 2023
EXAMPLE
a(0) = 1
a(1) = 1+2
a(2) = 1+2*3
a(3) = 1+2*3+4
a(4) = 1+2*3+4*5
a(5) = 1+2*3+4*5+6
a(6) = 1+2*3+4*5+6*7
a(7) = 1+2*3+4*5+6*7+8
a(8) = 1+2*3+4*5+6*7+8*9
MATHEMATICA
LinearRecurrence[{1, 3, -3, -3, 3, 1, -1}, {1, 3, 7, 11, 27, 33, 69}, 50] (* Harvey P. Dale, Jun 02 2019 *)
CROSSREFS
Cf. A002623.
Sequence in context: A024459 A001645 A103798 * A227364 A051202 A211674
KEYWORD
nonn,easy
AUTHOR
Jorge Coveiro, Apr 28 2004
EXTENSIONS
More terms from Ralf Stephan, Dec 02 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 April 15 20:47 EDT 2024. Contains 371696 sequences. (Running on oeis4.)