OFFSET
1,1
COMMENTS
Derangement here means the n-th element of L is not the n-th element of this sequence, so a(n) != 2n.
EXAMPLE
We must begin with 2,4,6,8,... and we cannot have a(1) = 2, so the first possibility is the label "24". The next term must be the smallest available label not leading to a contradiction, thus "6". The next one will be "8", etc. After the label "20" the smallest available label is "2". After this "2" we cannot have a(11) = 22 -- we thus take the smallest available label which is "224". No label is allowed to start with a leading zero.
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Eric Angelini, Sep 19 2004
EXTENSIONS
Corrected and extended by Jacques ALARDET and Eric Angelini, Aug 12 2008
Derangement wording introduced by Danny Rorabaugh, Nov 26 2015
STATUS
approved