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 A004739 Concatenation of sequences (1,2,2,..,n-1,n-1,n,n,n-1,n-1,..,2,2,1) for n >= 1. 5
 1, 1, 1, 2, 2, 1, 1, 2, 3, 3, 2, 1, 1, 2, 3, 4, 4, 3, 2, 1, 1, 2, 3, 4, 5, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 7, 6, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 9, 8, 7, 6, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 9, 8, 7 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Contribution from Artur Jasinski, Mar 07 2010: (Start) Zeta[2,k/p]+Zeta[2,(p-k)/p] = (Pi/Sin[(Pi*a(n))/p])2, where p=2,3,4, k=1..p-1. This sequence is odd subset of A003983 for odd p=3,5,7,9,.... For even subset of A003983 see A004737 (End) Table T(n,k) n, k > 0, T(n,k)=n-k+1, if n>=k, T(n,k)=k-n, if n < k.  Table read by sides of squares from T(1,n) to T(n,n), then from T(n,n) to T(n,1). General case A209301. Let m be natural number. The first column of the table T(n,1) is the sequence of the natural numbers A000027. In all columns with number k (k > 1) the segment with the length of (k-1): {m+k-2, m+k-3, ..., m}  shifts the sequence A000027. For m=1 the result is A004739, for m=2 the result is A004738, for m=3 the result is A209301. - Boris Putievskiy, Jan 24 2013 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Boris Putievskiy, Transformations [Of] Integer Sequences And Pairing Functions, arXiv preprint arXiv:1212.2732, 2012. F. Smarandache, Collected Papers, Vol. II F. Smarandache, Sequences of Numbers Involved in Unsolved Problems. Eric Weisstein's World of Mathematics, Smarandache Sequences FORMULA From Boris Putievskiy, Jan 24 2013: (Start) For the general case, a(n) = m*v+(2*v-1)*(t*t-n)+t, where t = floor((sqrt(n)-1/2)+1 and v = floor((n-1)/t)-t+1. For m=1, a(n ) = v+(2*v-1)*(t*t-n)+t, where t = floor((sqrt(n)-1/2)+1 and v = floor((n-1)/t)-t+1. (End) EXAMPLE From Boris Putievskiy, Jan 24 2013: (Start) The start of the sequence as table: 1..1..2..3..4..5..6... 2..1..1..2..3..4..5... 3..2..1..1..2..3..4... 4..3..2..1..1..2..3... 5..4..3..2..1..1..2... 6..5..4..3..2..1..1... 7..6..5..4..3..2..1... . . . The start of the sequence as triangle array read by rows: 1; 1,1,2; 2,1,1,2,3; 3,2,1,1,2,3,4; 4,3,2,1,1,2,3,4,5; 5,4,3,2,1,1,2,3,4,5,6; 6,5,4,3,2,1,1,2,3,4,5,6,7; . . . Row number r contains 2*r -1 numbers: r-1, r-2,...1,1,2,...r. (End) MATHEMATICA aa = {}; Do[Do[AppendTo[aa, (p/Pi) ArcSin[Sqrt[1/((1/Pi^2) (Zeta[2, k/p] + Zeta[2, (p - k)/p]))]]], {k, 1, p - 1}], {p, 3, 50, 2}]; Round[N[aa, 50]] (* Artur Jasinski, Mar 07 2010 *) PROG (Haskell) a004739 n = a004739_list !! (n-1) a004739_list = concat \$ map (\n -> [1..n] ++ [n, n-1..1]) [1..] -- Reinhard Zumkeller, Mar 26 2011 CROSSREFS Cf. A004737, A004738, A004731, A003983, A079813, A187760, A004738, A209301. Sequence in context: A136605 A165621 A284321 * A156282 A203776 A242357 Adjacent sequences:  A004736 A004737 A004738 * A004740 A004741 A004742 KEYWORD nonn,easy AUTHOR R. Muller EXTENSIONS More terms from Patrick De Geest, Jun 15 1998. STATUS approved

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Last modified April 22 10:13 EDT 2019. Contains 322330 sequences. (Running on oeis4.)