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 A080337 Bisection of A080107. 8
 1, 3, 12, 59, 339, 2210, 16033, 127643, 1103372, 10269643, 102225363, 1082190554, 12126858113, 143268057587, 1778283994284, 23120054355195, 314017850216371, 4444972514600178, 65435496909148513, 999907522895563403, 15832873029742458796, 259377550023571768075 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Number of symmetric positions of non-attacking rooks on upper-diagonal part of 2n X 2n chessboard. Number of length-n restricted growth strings (RGS) [s(0),s(1),...,s(n-1)] where s(0)=0 and s(k)<=2+max(prefix) for k>=1, see example. - Joerg Arndt, Apr 25 2010 Number of achiral color patterns in a row or loop of length 2n-1. Two color patterns are equivalent if the colors are permuted. - Robert A. Russell, Apr 24 2018 Stirling transform of A005425(n-1) per Knuth reference. - Robert A. Russell, Apr 28 2018 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..514 Joerg Arndt, Matters Computational (The Fxtbook), section 17.3.4, pp. 364-366. D. E. Knuth, The Art of Computer Programming, vol. 4A, Combinatorial Algorithms, Section 7.2.1.5 (p. 765). - Robert A. Russell, Apr 28 2018 J. Quaintance, Letter representations of rectangular m x n x p proper arrays, arXiv:math/0412244 [math.CO], 2004-2006. FORMULA Binomial transform of A002872 (sorting numbers). E.g.f.: exp(x+exp(x)+exp(2*x)/2-3/2) = exp(x+sum(j=1,2, (exp(j*x)-1)/j ) ). - Joerg Arndt, Apr 29 2011 From Robert A. Russell, Apr 24 2018: (Start) Aodd[n,k] = [n>1]*(k*Aodd[n-1,k]+Aodd[n-1,k-1]+Aodd[n-1,k-2])+[n==1]*[k==1] a(n) = Sum_{k=1..2n-1} Aodd[n,k]. (End) a(n) = Sum_{k=0..n} Stirling2(n, k)*A005425(k-1). (from Knuth reference) - Robert A. Russell, Apr 28 2018 EXAMPLE From Joerg Arndt, Apr 25 2010: (Start) For n=0 there is one empty string (term a(0)=0 not included here); for n=1 there is one string [0]; for n=2 there are 3 strings [00], [01], and [02]; for n=3 there are a(3)=12 strings (in lexicographic order): 01: [000], 02: [001], 03: [002], 04: [010], 05: [011], 06: [012], 07: [013], 08: [020], 09: [021], 10: [022], 11: [023], 12: [024]. (End) For a(3) = 12, both the row and loop patterns are AAAAA, AABAA, ABABA, ABBBA, AABCC, ABACA, ABBBC, ABCAB, ABCBA, ABCBD, ABCDA, and ABCDE. - Robert A. Russell, Apr 24 2018 MAPLE b:= proc(n, m) option remember; `if`(n=0, 1,       add(b(n-1, max(m, j)), j=1..m+2))     end: a:= n-> b(n, -1): seq(a(n), n=1..25);  # Alois P. Heinz, Jun 15 2018 MATHEMATICA Table[Sum[ Binomial[n, k] A002872[[k + 1]], {k, 0, n}], {n, 0, 24}] Aodd[m_, k_] := Aodd[m, k] = If[m > 1, k Aodd[m-1, k] + Aodd[m-1, k-1]   + Aodd[m-1, k-2], Boole[m==1 && k==1]] Table[Sum[Aodd[m, k], {k, 1, 2m-1}], {m, 1, 30}] (* Robert A. Russell, Apr 24 2018 *) x[n_] := x[n] = If[n<2, n+1, 2x[n-1] + (n-1) x[n-2]]; (* A005425 *) Table[Sum[StirlingS2[n, k] x[k-1], {k, 0, n}], {n, 30}] (* Robert A. Russell, Apr 28 2018, after Knuth reference *) PROG (PARI) x='x+O('x^66); egf=exp(x+exp(x)+exp(2*x)/2-3/2); /* = 1 +3*x +6*x^2 +59/6*x^3 +113/8*x^4 +... */ Vec(serlaplace(egf)) /* Joerg Arndt, Apr 29 2011 */ CROSSREFS Row sums of A140735. Cf. A002872, A080107. Column k=2 of A305962. Sequence in context: A192768 A179325 A064856 * A196710 A196711 A304788 Adjacent sequences:  A080334 A080335 A080336 * A080338 A080339 A080340 KEYWORD nonn AUTHOR Wouter Meeussen, Mar 18 2003 EXTENSIONS Comment corrected by Wouter Meeussen, Aug 14 2009 STATUS approved

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Last modified December 1 06:09 EST 2020. Contains 338833 sequences. (Running on oeis4.)