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 A057028 Triangle T read by rows: row n consists of the numbers C(n,2)+1 to C(n+1,2); numbers in odd-numbered 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 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 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

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Last modified January 16 23:44 EST 2019. Contains 319206 sequences. (Running on oeis4.)