

A249484


Sequence which reappears when consecutive terms are erased iff they have the same parity.


2



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
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OFFSET

0,2


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
Éric Angelini, More fractal triangles, SeqFan list, Jan 12 2015.


EXAMPLE

. n : 0123456789101112131415161718192021222324
. 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 .


PROG

(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


CROSSREFS

Cf. A249900.
Sequence in context: A011387 A019656 A256751 * A134017 A292285 A163984
Adjacent sequences: A249481 A249482 A249483 * A249485 A249486 A249487


KEYWORD

nonn


AUTHOR

Eric Angelini and Reinhard Zumkeller, Jan 13 2015


STATUS

approved



