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 A158405 Triangle T(n,m) = 1+2*m of odd numbers read along rows, 0<=m
 1, 1, 3, 1, 3, 5, 1, 3, 5, 7, 1, 3, 5, 7, 9, 1, 3, 5, 7, 9, 11, 1, 3, 5, 7, 9, 11, 13, 1, 3, 5, 7, 9, 11, 13, 15, 1, 3, 5, 7, 9, 11, 13, 15, 17, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Row sums are n^2 = A000290(n). The triangle sums, see A180662 for their definitions, link this triangle of odd numbers with seventeen different sequences, see the crossrefs. The knight sums Kn14 - Kn110 have been added. - Johannes W. Meijer, Sep 22 2010 A208057 is the eigentriangle of A158405 such that as infinite lower triangular matrices, A158405 * A208057 shifts the latter, deleting the right border of 1's. - Gary W. Adamson, Feb 22 2012 T(n,k) = A099375(n-1,n-k), 1<=k<=n. [Reinhard Zumkeller, Mar 31 2012] LINKS Seiichi Manyama, Rows n = 1..140, flattened Daniel Erman, The Josephus Problem, Numberphile video (2016) Boris Putievskiy, Transformations [of] Integer Sequences And Pairing Functions arXiv:1212.2732 [math.CO], 2012. FORMULA a(n)= 2*i-1, where i = n-t(t+1)/2, t = floor((-1+sqrt(8*n-7))/2). - Boris Putievskiy, Feb 03 2013 a(n)= 2*A002262(n-1) + 1. - Eric Werley, Sep 30 2015 EXAMPLE The triangle contains the first n odd numbers in row n: 1; 1,3; 1,3,5; 1,3,5,7; From Seiichi Manyama, Dec 02 2017: (Start)     |       a(n)        |                               | A000290(n)    -----------------------------------------------------------------    0|                                                      (=  0)    1|                 1 = 1/3 * ( 3)                       (=  1)    2|             1 + 3 = 1/3 * ( 5 +  7)                  (=  4)    3|         1 + 3 + 5 = 1/3 * ( 7 +  9 + 11)             (=  9)    4|     1 + 3 + 5 + 7 = 1/3 * ( 9 + 11 + 13 + 15)        (= 16)    5| 1 + 3 + 5 + 7 + 9 = 1/3 * (11 + 13 + 15 + 17 + 19)   (= 25) (End) MATHEMATICA Table[2 Range[1, n] - 1, {n, 12}] // Flatten (* Michael De Vlieger, Oct 01 2015 *) PROG (Haskell) a158405 n k = a158405_row n !! (k-1) a158405_row n = a158405_tabl !! (n-1) a158405_tabl = map reverse a099375_tabl -- Reinhard Zumkeller, Mar 31 2012 (PARI) a(n) = 2*(n-floor((-1+sqrt(8*n-7))/2)*(floor((-1+sqrt(8*n-7))/2)+1)/2)-1; vector(100, n, a(n)) \\ Altug Alkan, Oct 01 2015 CROSSREFS Cf. A129326, A099375, A005408. Triangle sums (see the comments): A000290 (Row1; Kn11 & Kn4 & Ca1 & Ca4 & Gi1 & Gi4); A000027 (Row2); A005563 (Kn12); A028347 (Kn13); A028560 (Kn14); A028566 (Kn15); A098603 (Kn16); A098847 (Kn17); A098848 (Kn18); A098849 (Kn19); A098850 (Kn110); A000217 (Kn21. Kn22, Kn23, Fi2, Ze2); A000384 (Kn3, Fi1, Ze3); A000212 (Ca2 & Ze4); A000567 (Ca3, Ze1); A011848 (Gi2); A001107 (Gi3). - Johannes W. Meijer, Sep 22 2010 Cf. A063656, A063657, A208057, A292610, A292611. Sequence in context: A130465 A272120 A194437 * A113759 A294966 A258208 Adjacent sequences:  A158402 A158403 A158404 * A158406 A158407 A158408 KEYWORD nonn,tabl,easy AUTHOR Paul Curtz, Mar 18 2009 EXTENSIONS Edited by R. J. Mathar, Oct 06 2009 STATUS approved

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Last modified June 26 04:11 EDT 2019. Contains 324369 sequences. (Running on oeis4.)