0,2

a(n+3) is the d=1 Betti number of the complement of '3-equal' arrangements in (n+3) dimensional real space, see Bj\"orner-Welker reference, Table I, page 308-9, column '1' with k=3, and Th. 5.2, p. 297-8.

Binomial transform of [1/2, 2/3, 3/4, 4/5...] = 1/2, 7/6, 31/12, 111/20, 351/30, 1023/42...; where 2, 6, 12, 20...= A002378 deleting the zero. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Apr 28 2005

H. Barcelo and R. Laubenbacher, Perspectives on A-homotopy theory and its applications, Discr. Math., 298 (2005), 39-61.

H. Barcelo and S. Smith, The discrete fundamental group of the order complex of B_n, Abstract 1020-05-141, 1020th Meeting Amer. Math. Soc., Cincinatti, Ohio, Oct 21-22, 2006.

A. Bj\"orner and V. Welker, The Homology of ''k-Equal'' Manifolds and Related Partition Lattices, Adv. Math. 110 (1995) 277-313.

a(n)= A055252(n+3, 3). a(n)= sum(a(j), j=0..n-1)+A045618(n), n >= 1.

a(n)= 2^n*(n^2+n+2)-1 (from welker(AT)Mathematik.Uni-Marburg.de, Jan 30 2001, see reference.)

G.f.: 1/(((1-2*x)^3)*(1-x)).

Partial sums of A001788 (without leading zero). - Paul Barry (pbarry(AT)wit.ie), Jun 26 2003

A001788(n)-A000337(n) - Jon Perry (perry(AT)globalnet.co.uk), Dec 12 2003

a(n) = A119258(n+4,n). - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), May 11 2006

Fourth column of triangle A055252.

Cf. A055252, A055249, A045618. Partial sums of A001788.

Cf. A000337, A001788, A066185.

Adjacent sequences: A055577 A055578 A055579 this_sequence A055581 A055582 A055583

Sequence in context: A119359 A055366 A109756 this_sequence A097786 A006458 A091344

easy,nonn

Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), May 26 2000; revised Feb 12, 2001.