Éric Angelini, <a href="http://list.seqfan.eu/pipermailoldermail/seqfan/2015-January/014291.html">More fractal triangles</a>, SeqFan list, Jan 12 2015.
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Sequence which is reappearing, reappears when consecutive terms are erased iff they have the same parity.
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Cf. A249900.
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Éric Angelini, <a href="http://list.seqfan.eu/pipermail/seqfan/2015-January/014291.html">More fractal triangles</a>, SeqFan list, Jan 12 2015.
. n : 0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17|18|19|20|21|22|23|24|
. a(n): 1 2 4 3 5 2 7 9 4 3 6 8 5 2 7 10 12 9 4 3 6 11 13 8 5
. 0/1 : 1 0 0 1 1 0 1 1 0 1 0 0 1 0 1 0 0 1 0 1 0 1 1 0 1
. : 1 _ _ _ _ 2 _ _ 4 3 _ _ 5 2 7 _ _ 9 4 3 6 _ _ 8 5 .
(Haskell)
a249484 n = a249484_list !! n
a249484_list = 1 : concat (zipWith (++) ([2] : f [5, 2, 7]) (f [4, 3])) where
f = iterate (\row -> [g $ head row] ++ row ++ [g $ last row])
g x = x + ((5 -) . (* 2) . flip mod 2) x
_Eric Angelini_ and _Reinhard Zumkeller_, Jan 13 2015
allocated for Reinhard ZumkellerSequence which is reappearing, when consecutive terms are erased iff they have the same parity.
1, 2, 4, 3, 5, 2, 7, 9, 4, 3, 6, 8, 5, 2, 7, 10, 12, 9, 4, 3, 6, 11, 13, 8, 5, 2, 7, 10, 15, 17, 12, 9, 4, 3, 6, 11, 14, 16, 13, 8, 5, 2, 7, 10, 15, 18, 20, 17, 12, 9, 4, 3, 6, 11, 14, 19, 21, 16, 13, 8, 5, 2, 7, 10, 15, 18, 23, 25, 20, 17, 12, 9, 4, 3, 6
0,2
Reinhard Zumkeller, <a href="/A249484/b249484.txt">Table of n, a(n) for n = 0..10000</a>
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nonn
Reinhard Zumkeller, Jan 13 2015
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allocated for Reinhard Zumkeller
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