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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A178901 a(1)=2; for n > 1, a(n) is the largest number <= 2*a(n-1) divisible by n. 1
2, 4, 6, 12, 20, 36, 70, 136, 270, 540, 1078, 2148, 4290, 8568, 17130, 34256, 68510, 137016, 274018, 548020, 1096032, 2192058, 4384099, 8768184, 17536350, 35072700, 70145379, 140290752, 280581496, 561162990, 1122325953, 2244651904 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The definition "a(1)=1; for n > 1, a(n) is the largest number <= 2*a(n-1) divisible by n" produces the natural numbers 1,2,3,4,5,...

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

2*36=72. But 72 is not a multiple of 7, so we must look for the largest multiple of 7 <= 72, and this is 70.

MAPLE

A178901 := proc(n) option remember; if n =1 then 2; else for a from 2*procname(n-1) by -1 do if a mod n = 0 then return a; end if; end do: end if; end proc: seq(A178901(n), n=1..30) ; # R. J. Mathar, Jun 26 2010

CROSSREFS

Sequence in context: A294429 A107383 A078025 * A164146 A279245 A090906

Adjacent sequences:  A178898 A178899 A178900 * A178902 A178903 A178904

KEYWORD

nonn

AUTHOR

J. Lowell, Jun 21 2010

EXTENSIONS

a(8)-a(32) from Robert G. Wilson v and John W. Layman, Jun 28 2010

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 October 19 11:09 EDT 2019. Contains 328216 sequences. (Running on oeis4.)