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 A246694 Triangle t(n,k) = t(n,k-2) + 1 if n > 1 and 2 <= k <= n; t(0,0) = 1, t(1,0) = 1, t(1,1) = 2; if n > 1 is odd, then t(n,0) = t(n-1,n-2) + 1 and t(n,1) = t(n-1,n-1) + 1; if n > 1 is even, then t(n,0) = t(n-1,n-1) + 1 and t(n,1) = t(n-1,n-2) + 1. 6
 1, 1, 2, 3, 2, 4, 3, 5, 4, 6, 7, 5, 8, 6, 9, 7, 10, 8, 11, 9, 12, 13, 10, 14, 11, 15, 12, 16, 13, 17, 14, 18, 15, 19, 16, 20, 21, 17, 22, 18, 23, 19, 24, 20, 25, 21, 26, 22, 27, 23, 28, 24, 29, 25, 30, 31, 26, 32, 27, 33, 28, 34, 29, 35, 30, 36, 31, 37, 32 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS As an array, for each m, row 2*m has m odd numbers and m+1 even numbers; row 2*m-1 has m odds and m evens.  As a sequence, every positive integer n occurs exactly twice, separated by floor((n+1)/2) other numbers. LINKS Reinhard Zumkeller, Rows n = 0..125 of triangle, flattened EXAMPLE First 8 rows: 1 1 ... 2 3 ... 2 ... 4 3 ... 5 ... 4 ... 6 7 ... 5 ... 8 ... 6 ... 9 7 ... 10 .. 8 ... 11 .. 9 ... 12 13 .. 10 .. 14 .. 11 .. 15 .. 12 .. 16 13 .. 17 .. 14 .. 18 .. 15 .. 19 .. 16 .. 20 MATHEMATICA z = 25; t[0, 0] = 1; t[1, 0] = 1; t[1, 1] = 2; t[n_, 0] := If[OddQ[n], t[n - 1, n - 2] + 1, t[n - 1, n - 1] + 1]; t[n_, 1] := If[OddQ[n], t[n - 1, n - 1] + 1, t[n - 1, n - 2] + 1]; t[n_, k_] := t[n, k - 2] + 1; Flatten[Table[t[n, k], {n, 0, z}, {k, 0, n}]](*A246694*) PROG (Haskell) a246694 n k = a246694_tabl !! n !! k a246694_row n = a246694_tabl !! n a246694_tabl = [1] : [1, 2] : f 1 2 [1, 2] where    f i z xs = ys : f j (z + 1) ys where      ys = take (z + 1) \$ map (+ 1) (xs !! (z - i) : xs !! (z - j) : ys)      j = 3 - i -- Reinhard Zumkeller, Sep 03 2014 CROSSREFS Cf. A246705, A246706, A246696. Cf. A246695 (row sums), A174114 (central terms). Sequence in context: A264116 A283368 A199474 * A054384 A026400 A026409 Adjacent sequences:  A246691 A246692 A246693 * A246695 A246696 A246697 KEYWORD nonn,easy,tabl AUTHOR Clark Kimberling, Sep 01 2014 EXTENSIONS Edited by M. F. Hasler, Nov 17 2014 STATUS approved

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Last modified November 17 22:58 EST 2018. Contains 317279 sequences. (Running on oeis4.)