The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A135922 Inverse binomial transform of A006116, which is the sum of Gaussian binomial coefficients [n,k] for q=2. 8
 1, 1, 2, 6, 26, 158, 1330, 15414, 245578, 5382862, 162700898, 6801417318, 394502066810, 31849226170622, 3589334331706258, 566102993389615254, 125225331231990004138, 38920655753545108286254, 17021548688670112527781058, 10486973328106497739526535366 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Let v_1,...,v_n be a basis of an n-dimensional vector space V over the field GF(2).  Then a(n+1) is the number of subspaces of V that contain the vector v_1 but do not contain v_2,...,v_n. - Geoffrey Critzer, Jul 05 2018 Also number of Stanley graphs on n nodes. For precise definition see Knuth (1997). - Alois P. Heinz, Sep 24 2019 REFERENCES S. R. Finch, Mathematical Constants, Cambridge, 2003, p. 318. LINKS Alois P. Heinz, Table of n, a(n) for n = 0..115 D. E. Knuth, Letter to Daniel Ullman and others, Apr 29 1997 [Annotated scanned copy, with permission] Zvi Rosen, Yan X. Zhang, Convex Neural Codes in Dimension 1, arXiv:1702.06907 [math.CO], 2017. Mentions this sequence. FORMULA O.g.f.: A(x) = Sum_{n>=0} x^n / Product_{k=0..n} (1 - (2^k-1)*x). G.f.: (G(0) - 1)/(x-1) where G(k) =  1 - 1/(1-x*(2^k-1))/(1-x/(x-1/G(k+1) )); (recursively defined continued fraction). - Sergei N. Gladkovskii, Jan 16 2013 a(n) ~ c * 2^(n^2/4), where c = EllipticTheta[3,0,1/2]/QPochhammer[1/2,1/2] = 7.3719688014613... if n is even and c = EllipticTheta[2,0,1/2]/QPochhammer[1/2,1/2] = 7.3719494907662... if n is odd. - Vaclav Kotesovec, Aug 23 2013 a(n) = Sum_{k=0..n} qStirling2(n,k), where qStirling2 is the triangle A139382. - Vladimir Kruchinin, Feb 26 2020 EXAMPLE O.g.f.: A(x) = 1 + x/(1-x) + x^2/((1-x)*(1-3x)) + x^3/((1-x)*(1-3x)*(1-7x)) + x^4/((1-x)*(1-3x)*(1-7x)*(1-15x)) + ... MAPLE b:= proc(n) option remember; add(mul(       (2^(i+k)-1)/(2^i-1), i=1..n-k), k=0..n)     end: a:= proc(n) option remember;       add(b(n-j)*binomial(n, j)*(-1)^j, j=0..n)     end: seq(a(n), n=0..19);  # Alois P. Heinz, Sep 24 2019 MATHEMATICA Table[SeriesCoefficient[Sum[x^n/Product[(1-(2^k-1)*x), {k, 0, n}], {n, 0, nn}], {x, 0, nn}] , {nn, 0, 20}] (* Vaclav Kotesovec, Aug 23 2013 *) b[n_] := b[n] = Sum[Product[(2^(i+k)-1)/(2^i-1), {i, 1, n-k}], {k, 0, n}]; a[n_] := a[n] = Sum[(-1)^j b[n-j] Binomial[n, j], {j, 0, n}]; a /@ Range[0, 19] (* Jean-François Alcover, Mar 10 2020, after Alois P. Heinz *) PROG (PARI) a(n)=polcoeff(sum(k=0, n, x^k/prod(j=0, k, 1-(2^j-1)*x+x*O(x^n))), n) (Sage) # After Vladimir Kruchinin. def a(n):     @cached_function     def T(n, k):         if k == 1 or k == n: return 1         return (2^k-1)*T(n-1, k) + T(n-1, k-1)     return sum(T(n, k) for k in (1..n)) if n > 0 else 1 print([a(n) for n in (0..19)]) # Peter Luschny, Feb 26 2020 CROSSREFS Cf. A006116, A323841, A323842, A323843, A139382. Sequence in context: A099758 A099760 A112934 * A213430 A103367 A047863 Adjacent sequences:  A135919 A135920 A135921 * A135923 A135924 A135925 KEYWORD nonn AUTHOR Paul D. Hanna, Dec 06 2007 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 31 19:40 EDT 2020. Contains 334748 sequences. (Running on oeis4.)