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A097481
Write the positive even integers on labels in numerical order, forming an infinite sequence L. Consider the succession of digits of L: 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0 ... (A036211). This sequence gives a derangement of L that produces the same succession of digits, subject to the constraint that the smallest unused label must be used that does not lead to a contradiction.
2
24, 6, 8, 10, 12, 14, 16, 18, 20, 2, 224, 26, 28, 30, 32, 34, 36, 38, 40, 4, 244, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132
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
Sequence in context: A215752 A111803 A091737 * A267744 A040559 A339007
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