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 A054341 Row sums of triangle A054336 (central binomial convolutions). 11
 1, 2, 5, 12, 30, 74, 185, 460, 1150, 2868, 7170, 17904, 44760, 111834, 279585, 698748, 1746870, 4366460, 10916150, 27287944, 68219860, 170541252, 426353130, 1065853432, 2664633580, 6661479944, 16653699860, 41633878200, 104084695500 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) = # Dyck (n+1)-paths all of whose components are symmetric. A strict Dyck path is one with exactly one return to ground level (necessarily at the end). Every nonempty Dyck path is expressible uniquely as a concatenation of one or more strict Dyck paths, called its components. - David Callan, Mar 02 2005 a(n) = # 2-Motzkin paths (i.e. Motzkin paths with blue and red level steps) with no level steps at positive height. Example: a(2)=5 because, denoting U=(1,1), D=(1,-1), B=blue (1,0), R=red (1,0), we have BB, BR, RB, RR, and UD. - Emeric Deutsch, Jun 07 2011 Inverse Chebyshev transform of the second kind applied to 2^n. This maps g(x)->c(x^2)g(xc(x^2)). - Paul Barry, Sep 14 2005 Hankel transform of this sequence gives A000012 = [1,1,1,1,1,1,1,...]. - Philippe Deléham, Oct 24 2007 Inverse binomial transform of A059738. - Philippe Deléham, Nov 24 2009 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 J. W. Layman, The Hankel Transform and Some of its Properties, J. Integer Sequences, 4 (2001), #01.1.5. FORMULA a(n) = sum(A054336(n, m), m=0..n). G.f.: 1/(1-2*x-x^2*c(x^2)), where c(x) = g.f. for Catalan numbers A000108. G.f.: c(x^2)/(1-2*x*c(x^2)); a(n)=sum{k=0..n, C(n, (n-k)/2)(1+(-1)^(n+k))2^k*(k+1)/(n+k+2)}. - Paul Barry, Sep 14 2005 G.f.: 2/(1-4*x+sqrt(1-4*x^2)). - Ira M. Gessel, Oct 27 2013 a(n) = A127358(n+1)-2*A127358(n). - Philippe Deléham, Mar 02 2007 a(n) = A126075(n,0). - Philippe Deléham, Nov 24 2009 a(n) = Sum_{k, 0<=k<=n} A053121(n,k)*2^k. - Philippe Deléham, Nov 28 2009 a(n) is the upper left term of M^n, M = an infinite square production matrix as follows: 2, 1, 0, 0, 0,... 1, 0, 2, 0, 0,... 0, 1, 0, 1, 0,... 0, 0, 1, 0, 1,... 0, 0, 0, 1, 0,... ... - Gary W. Adamson, Sep 07 2011 Conjecture: 2*(n+1)*a(n) +5*(-n-1)*a(n-1) +8*(-n+2)*a(n-2) +20*(n-2)*a(n-3)=0. - R. J. Mathar, Nov 30 2012 a(n) ~ 3 * 5^n / 2^(n+2). - Vaclav Kotesovec, Feb 13 2014 EXAMPLE a(4) = 30, the upper left term of M^4. MATHEMATICA CoefficientList[Series[2/(1-4*x+Sqrt[1-4*x^2]), {x, 0, 20}], x] (* Vaclav Kotesovec, Feb 13 2014 *) CROSSREFS Cf. A000108, A054336. Sequence in context: A062423 A118649 A033482 * A000106 A076883 A140832 Adjacent sequences:  A054338 A054339 A054340 * A054342 A054343 A054344 KEYWORD easy,nonn AUTHOR Wolfdieter Lang, Mar 13 2000 STATUS approved

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Last modified October 22 02:46 EDT 2018. Contains 316431 sequences. (Running on oeis4.)