This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A079500 #115 Sep 09 2022 04:25:18 %S A079500 1,1,2,3,5,8,14,24,43,77,140,256,472,874,1628,3045,5719,10780,20388, %T A079500 38674,73562,140268,268066,513350,984911,1892875,3643570,7023562, %U A079500 13557020,26200182,50691978,98182666,190353370,369393466,717457656,1394632365,2713061899 %N A079500 Number of compositions of the integer n in which the first part is >= the other parts. %C A079500 Essentially the same as A007059: a(n) = A007059(n+1). %C A079500 In lunar arithmetic in base 2, this is the number of lunar divisors of the number 111...1 (with n 1's). E.g., 1111 has a(4) = 5 divisors (see A048888). - _N. J. A. Sloane_, Feb 23 2011. %C A079500 First differences of A186537. - _N. J. A. Sloane_, Feb 23 2011 %C A079500 Number of balanced ordered rooted trees with n non-root nodes (see A048816 for unordered balanced trees); see example. The compositions are obtained from the level sequences by identifying a length-k run of (non-root) levels [t, t+1, t+2, ..., t+k-1] with a part k. - _Joerg Arndt_, Jul 20 2014 %D A079500 Arnold Knopfmacher and Neville Robbins, Compositions with parts constrained by the leading summand, Ars Combin. 76 (2005), 287-295. %H A079500 Alois P. Heinz, <a href="/A079500/b079500.txt">Table of n, a(n) for n = 0..2000</a> (first 400 terms from T. D. Noe) %H A079500 D. Applegate, M. LeBrun and N. J. A. Sloane, <a href="http://arxiv.org/abs/1107.1130">Dismal Arithmetic</a>, arXiv:1107.1130 [math.NT], 2011. [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing] %H A079500 D. Applegate, M. LeBrun, N. J. A. Sloane, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Sloane/carry2.html">Dismal Arithmetic</a>, J. Int. Seq. 14 (2011) # 11.9.8. %H A079500 Srecko Brlek, Andrea Frosini, Simone Rinaldi, and Laurent Vuillon, <a href="https://doi.org/10.37236/1041">Tilings by translation: enumeration by a rational language approach</a>, The Electronic Journal of Combinatorics, vol.13, (2006). %H A079500 A. Frosini and S. Rinaldi, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL9/Frosini/fros2.html">On the Sequence A079500 and Its Combinatorial Interpretations</a>, Journal of Integer Sequences, Vol. 9 (2006), Article 06.3.1. %H A079500 R. Kemp, <a href="http://dx.doi.org/10.1002/rsa.3240050111">Balanced ordered trees</a>, Random Structures Algorithms, 5 (1994), pp. 99-121. %H A079500 <a href="/index/Di#dismal">Index entries for sequences related to dismal (or lunar) arithmetic</a> %F A079500 G.f.: (1-z) * Sum_{k>=0} z^k/(1 - 2*z + z^(k+1)). %F A079500 a(n) = A048888(n) - 1. %F A079500 This is a subsequence of A067399: a(n) = A067399(2^n-1). %F A079500 G.f.: -((1 + x^2 + 1/(x-1))/x)*( 1 + x*(x-1)^3*(1-x+x^3)/( Q(0) - x*(x-1)^3*(1-x+x^3)) ), where Q(k) = (x+1)*(2*x-1)*(1-x)^2 + x^(k+2)*(x+x^2+x^3-2*x^4-1 - x^(k+3) + x^(k+5)) - x*(-1+2*x-x^(k+3))*(1-2*x+x^2+x^(k+4)-x^(k+5))*(-1+4*x-5*x^2+2*x^3 - x^(k+2)- x^(k+5) + 2*x^(k+3) - x^(2*k+5) + x^(2*k+6))/Q(k+1) ; (continued fraction). - _Sergei N. Gladkovskii_, Dec 14 2013 %F A079500 a(n) = Sum_{j=1..n} F(j, n+1-j), where F(n,k) is the n-th k-generalized Fibonacci number A092921(k,n). - _Gregory L. Simay_, Aug 21 2022 %e A079500 From _Joerg Arndt_, Dec 29 2012: (Start) %e A079500 There are a(7)=24 compositions p(1)+p(2)+...+p(m)=7 such that p(k) <= p(1): %e A079500 [ 1] [ 1 1 1 1 1 1 1 ] %e A079500 [ 2] [ 2 1 1 1 1 1 ] %e A079500 [ 3] [ 2 1 1 1 2 ] %e A079500 [ 4] [ 2 1 1 2 1 ] %e A079500 [ 5] [ 2 1 2 1 1 ] %e A079500 [ 6] [ 2 1 2 2 ] %e A079500 [ 7] [ 2 2 1 1 1 ] %e A079500 [ 8] [ 2 2 1 2 ] %e A079500 [ 9] [ 2 2 2 1 ] %e A079500 [10] [ 3 1 1 1 1 ] %e A079500 [11] [ 3 1 1 2 ] %e A079500 [12] [ 3 1 2 1 ] %e A079500 [13] [ 3 1 3 ] %e A079500 [14] [ 3 2 1 1 ] %e A079500 [15] [ 3 2 2 ] %e A079500 [16] [ 3 3 1 ] %e A079500 [17] [ 4 1 1 1 ] %e A079500 [18] [ 4 1 2 ] %e A079500 [19] [ 4 2 1 ] %e A079500 [20] [ 4 3 ] %e A079500 [21] [ 5 1 1 ] %e A079500 [22] [ 5 2 ] %e A079500 [23] [ 6 1 ] %e A079500 [24] [ 7 ] %e A079500 (End) %e A079500 From _Joerg Arndt_, Jul 20 2014: (Start) %e A079500 The a(7) = 24 balanced ordered rooted trees with 7 non-root nodes are, as level sequences (of the pre-order walk): %e A079500 01: [ 0 1 1 1 1 1 1 1 ] %e A079500 02: [ 0 1 2 1 2 1 2 2 ] %e A079500 03: [ 0 1 2 1 2 2 1 2 ] %e A079500 04: [ 0 1 2 1 2 2 2 2 ] %e A079500 05: [ 0 1 2 2 1 2 1 2 ] %e A079500 06: [ 0 1 2 2 1 2 2 2 ] %e A079500 07: [ 0 1 2 2 2 1 2 2 ] %e A079500 08: [ 0 1 2 2 2 2 1 2 ] %e A079500 09: [ 0 1 2 2 2 2 2 2 ] %e A079500 10: [ 0 1 2 3 1 2 3 3 ] %e A079500 11: [ 0 1 2 3 2 3 2 3 ] %e A079500 12: [ 0 1 2 3 2 3 3 3 ] %e A079500 13: [ 0 1 2 3 3 1 2 3 ] %e A079500 14: [ 0 1 2 3 3 2 3 3 ] %e A079500 15: [ 0 1 2 3 3 3 2 3 ] %e A079500 16: [ 0 1 2 3 3 3 3 3 ] %e A079500 17: [ 0 1 2 3 4 2 3 4 ] %e A079500 18: [ 0 1 2 3 4 3 4 4 ] %e A079500 19: [ 0 1 2 3 4 4 3 4 ] %e A079500 20: [ 0 1 2 3 4 4 4 4 ] %e A079500 21: [ 0 1 2 3 4 5 4 5 ] %e A079500 22: [ 0 1 2 3 4 5 5 5 ] %e A079500 23: [ 0 1 2 3 4 5 6 6 ] %e A079500 24: [ 0 1 2 3 4 5 6 7 ] %e A079500 (End) %e A079500 From _Gus Wiseman_, Oct 07 2018: (Start) %e A079500 The a(0) = 1 through a(6) = 14 balanced rooted plane trees: %e A079500 o (o) (oo) (ooo) (oooo) (ooooo) (oooooo) %e A079500 ((o)) ((oo)) ((ooo)) ((oooo)) ((ooooo)) %e A079500 (((o))) (((oo))) (((ooo))) (((oooo))) %e A079500 ((o)(o)) ((o)(oo)) ((o)(ooo)) %e A079500 ((((o)))) ((oo)(o)) ((oo)(oo)) %e A079500 ((((oo)))) ((ooo)(o)) %e A079500 (((o)(o))) ((((ooo)))) %e A079500 (((((o))))) (((o)(oo))) %e A079500 (((oo)(o))) %e A079500 ((o)(o)(o)) %e A079500 (((((oo))))) %e A079500 ((((o)(o)))) %e A079500 (((o))((o))) %e A079500 ((((((o)))))) %e A079500 (End) %p A079500 M:=101: %p A079500 t1:=add( (1-x)*x^k/(1-2*x+x^k), k=1..M): %p A079500 series(t1,x,M-1); %p A079500 seriestolist(%); %p A079500 # second Maple program: %p A079500 b:= proc(n, m) option remember; `if`(n=0, 1, %p A079500 `if`(m=0, add(b(n-j, j), j=1..n), %p A079500 add(b(n-j, min(n-j, m)), j=1..min(n, m)))) %p A079500 end: %p A079500 a:= n-> b(n, 0): %p A079500 seq(a(n), n=0..40); # _Alois P. Heinz_, May 01 2014 %t A079500 nn=36;CoefficientList[Series[Sum[x^i/(1-(x-x^(i+1))/(1-x)),{i,0,nn}],{x,0,nn}],x] (* _Geoffrey Critzer_, Mar 12 2013 *) %t A079500 b[n_, m_] := b[n, m] = If[n==0, 1, If[m==0, Sum[b[n-j, j], {j, 1, n}], Sum[ b[n-j, Min[n-j, m]], {j, 1, Min[n, m]}]]]; a[n_] := b[n, 0]; Table[a[n], {n, 0, 40}] (* _Jean-François Alcover_, Nov 23 2015, after _Alois P. Heinz_ *) %Y A079500 Cf. A188541. %Y A079500 Cf. A000081 A000311, A001678, A120803, A320154, A320160, A316624, A320169. %Y A079500 Cf. A092921. %K A079500 nonn %O A079500 0,3 %A A079500 _Arnold Knopfmacher_, Jan 21 2003 %E A079500 Offset corrected by _N. J. A. Sloane_, Feb 23 2011 %E A079500 More terms from _N. J. A. Sloane_, Feb 24 2011 %E A079500 Further edits (required in order to clarify the definition - is the first part >= the rest. or only > the rest? Answer: the former; for the latter, see A007059) by _N. J. A. Sloane_, May 08 2011