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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A285884 For n => 1, the number of distinct summands u and v that can be used in the representation of n as u+v, where u and v are two (possibly equal) Ulam numbers A002858. 0
0, 1, 2, 3, 4, 3, 4, 3, 4, 4, 2, 5, 2, 6, 4, 3, 6, 2, 8, 4, 4, 5, 0, 6, 0, 3, 4, 2, 8, 4, 4, 5, 0, 6, 0, 3, 4, 2, 8, 4, 4, 6, 0, 8, 0, 4, 2, 2, 8, 4, 6, 5, 2, 10, 4, 7, 2, 4, 6, 4, 6, 2, 6, 10, 6, 8, 0, 4, 2, 6, 4, 3, 10, 6, 10, 5, 2, 6, 4, 8, 4, 2, 10, 4, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

An odd number in the sequence means that there exists the "pseudo-representation" u + u, where u is an Ulam number. For example, a(22)=5 since 22 = 18 + 4 = 16 + 6 = 11 + 11, and the 5 distinct summands 18,4,16,6,11 are Ulam numbers.

Note that both 2 and 3 are values for Ulam numbers since, by the previous comment, a value of 3 means that the Ulam number has the additional "pseudo-representation" u + u (see the Examples).

It seems that all nonnegative integers occur as values of this sequence.

LINKS

Table of n, a(n) for n=1..85.

EXAMPLE

a(23) = 0 since 23 can't be written as the sum of two distinct Ulam numbers. This type of numbers are in A033629.

a(94) = 1 since 94 = 47 + 47, where 47 is an Ulam number.  This type of numbers are in A287611.

a(11) = 2 since 11 has the unique representation 11 = 8 + 3, where 8,3 are Ulam numbers. If such n is also an Ulam number (such as 11), then it is in A002858.

a(8) = 3 since it has the representation 8 = 6 + 2 and also the additional "pseudo-representation" 8 = 4 + 4, where 6, 2, and 4 are Ulam numbers. If n has such a "pseudo-representation" and is an Ulam number, then it is in A068799.

CROSSREFS

Cf. A002858, A068799, A033629, A287611.

Sequence in context: A182101 A242289 A158515 * A123709 A165482 A323242

Adjacent sequences:  A285881 A285882 A285883 * A285885 A285886 A285887

KEYWORD

nonn

AUTHOR

Enrique Navarrete, Apr 27 2017

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 21 22:47 EDT 2019. Contains 328315 sequences. (Running on oeis4.)