Problem 44321. Van Eck's Sequence's nth member

Created by Mehmet OZC

Solve Later

{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Return the Van Eck's Sequence's nth member.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>For detailed info :</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"http://oeis.org/A181391\"><w:r><w:t>OEIS link</w:t></w:r></w:hyperlink><w:r><w:t> and</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"https://www.theguardian.com/science/alexs-adventures-in-numberland/2014/oct/07/neil-sloane-the-man-who-loved-only-integer-sequences\"><w:r><w:t>here</w:t></w:r></w:hyperlink></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ seq = 0, 0, 1, 0, 2, 0, 2, 2, 1, 6, 0, 5...]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>First member is 0;</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Second member is 0;</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>third member is 1 etc</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

Solve

Solution Stats

819 Solutions
307 Solvers

Last Solution submitted on Oct 01, 2022

Last 200 Solutions

Problem Comments

1 Comment

1 Comment

Huajie Zheng on 23 Oct 2018

interesting

Solution Comments

Solution 1427667

2 Comments

2 Comments

Simone Sabbatini on 29 Jan 2018

I don't understand why in my Matlab software it works for all the x while here it falis for x>=11

function result = VanEcksSequence(n)
A=0;
for i=1:n
if i==1
A(i+1)=0;
else
[C Chigh]=ismember(A(i),A(1:i-1));
if not(Chigh==0)
A(i+1)=i-Chigh;
else
A(i+1) = 0;
end
end
end
result = A(n);
end

Asif Newaz on 15 Dec 2019

@Simone Sabbatini
i dont think ur algorithm is correct. understand the sequence well..
The first term is zero. Then-
If the last term is *new* to the sequence so far then-- The next term is zero.
Otherwise:
The next term is "how far back" this last term occured previousely.

Solution 1305517

1 Comment

1 Comment

Dyuman Joshi on 8 Sep 2021

Quite an innovative way lol

Problem Recent Solvers307

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 44321. Van Eck's Sequence's nth member

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers307

Suggested Problems

More from this Author92

Problem Tags

Community Treasure Hunt

Problem 44321. Van Eck's Sequence's nth member

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers307

Suggested Problems

More from this Author92

Problem Tags

Community Treasure Hunt

Players