

A057028


Triangle T read by rows: row n consists of the numbers C(n,2)+1 to C(n+1,2); numbers in oddnumbered places form a decreasing sequence and the others an increasing sequence.


5



1, 3, 2, 5, 6, 4, 9, 8, 10, 7, 13, 14, 12, 15, 11, 19, 18, 20, 17, 21, 16, 25, 26, 24, 27, 23, 28, 22, 33, 32, 34, 31, 35, 30, 36, 29, 41, 42, 40, 43, 39, 44, 38, 45, 37, 51, 50, 52, 49, 53, 48, 54, 47, 55, 46, 61, 62, 60, 63, 59, 64, 58, 65, 57, 66, 56
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OFFSET

1,2


LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000
Index entries for sequences that are permutations of the natural numbers


EXAMPLE

Rows: 1; 3,2; 5,6,4; 9,8,10,7; ...


MATHEMATICA

nn = 12; t = Table[Range[Binomial[n, 2] + 1, Binomial[n + 1, 2]], {n, nn}]; Reverse /@ Table[t[[n, If[OddQ@ k, Ceiling[k/2], k/2] ]], {n, nn}, {k, n}] // Flatten (* Michael De Vlieger, Jul 02 2016 *)


CROSSREFS

Reflection of the array in A057027 about its central column, a permutation of the natural numbers.
Inverse permutation: A064789.
Sequence in context: A084493 A084497 A120912 * A195112 A276618 A293722
Adjacent sequences: A057025 A057026 A057027 * A057029 A057030 A057031


KEYWORD

nonn,tabl


AUTHOR

Clark Kimberling, Jul 28, 2000


STATUS

approved



