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 A215342 Expansion of series reversion of x*(1-x^3*sum(k>=1, x^k)). 2
 1, 0, 0, 0, 1, 1, 1, 1, 6, 12, 19, 27, 71, 166, 329, 579, 1222, 2756, 5921, 11754, 24179, 52372, 114031, 239726, 502269, 1074961, 2333143, 5017552, 10714567, 23006558, 49861081, 108122488, 233691980, 505329915, 1097463037, 2389325284, 5199960642, 11314793335, 24663217250, 53864633059 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,9 COMMENTS Dissections (using non-intersecting diagonals) of a convex (n+1)-gon into k-gons where k>=6. [Joerg Arndt, Feb 15 2014] LINKS Vaclav Kotesovec, Table of n, a(n) for n = 1..250 Alison Schuetz, Gwyneth Whieldon, Polygonal Dissections and Reversions of Series, arXiv:1401.7194 [math.CO] D. Birmajer, J. B. Gil, M. D. Weiner, Colored partitions of a convex polygon by noncrossing diagonals, arXiv preprint arXiv:1503.05242 [math.CO], 2015. FORMULA Recurrence: 283*(n-3)*(n-2)*(n-1)*n*(14438110231*n^6 - 346214993274*n^5 + 3438949212625*n^4 - 18105364836570*n^3 + 53265099505324*n^2 - 82987438028496*n + 53465930027280)*a(n) = (n-3)*(n-2)*(n-1)*(5399853226394*n^7 - 137584187324067*n^6 + 1483504918415939*n^5 - 8763694066910355*n^4 + 30585682233578711*n^3 - 62946796681030518*n^2 + 70573456271906136*n - 33158656683118080)*a(n-1) - (n-3)*(n-2)*(534210078547*n^8 - 14946795065326*n^7 + 180235890644998*n^6 - 1221993860476624*n^5 + 5087726442447403*n^4 - 13295664719568394*n^3 + 21246368278875372*n^2 - 18919520411340456*n + 7154560952974080)*a(n-2) - 5*(n-4)*(n-3)*(28876220462*n^8 - 793496758165*n^7 + 9354947999333*n^6 - 61627542806839*n^5 + 247116200695877*n^4 - 613894185501244*n^3 + 913857055091496*n^2 - 732955177968120*n + 234541607788800)*a(n-3) + 5*(9947857949159*n^10 - 357916425755694*n^9 + 5753280746412201*n^8 - 54388490463504720*n^7 + 334719732595671573*n^6 - 1400557913088383070*n^5 + 4032929135663406319*n^4 - 7886242788829977540*n^3 + 10015113186875731788*n^2 - 7452248915385205056*n + 2464721951024954880)*a(n-4) - 8*(n-5)*(2*n - 9)*(4*n - 21)*(4*n - 19)*(14438110231*n^6 - 259586331888*n^5 + 1924445899720*n^4 - 7522955714190*n^3 + 16337121992089*n^2 - 18661982982042*n + 8745398997120)*a(n-5). - Vaclav Kotesovec, Mar 22 2014 a(n) ~ s*sqrt((3*r*s+r-4)/(5*(3*r*s-2*r-2))) / (2*sqrt(Pi) * n^(3/2) * r^(n-1)), where s = 1.1954869989505368389... is the root of the equation 64 - 897*s + 2460*s^2 - 2787*s^3 + 1442*s^4 - 283*s^5 = 0, and r = (4*s-5)/(s*(3*s-4)) = 0.441061092405258554919... - Vaclav Kotesovec, Mar 23 2014 G.f. A(x) for offset 0 satisfies 1-(1+x)*A(x) + x*A(x)^2 + x^4*A(x)^5 = 0. - Vaclav Kotesovec, Mar 23 2014 EXAMPLE Use the Lang and the Abramowitz and Stegun links in A111785. In the A-S list of partitions of the integer n on page 831 null all partitions containing 1, 2, or 3. These correspond to the null coefficients of x^2, x^3, and x^4 in the series to be reverted and to 3-, 4-, and 5-gons not being allowed in the dissections. a(9)=6 corresponds to the A-S partitions (n=8,m=1, partition 1)=8 and (8,2,4)=4^2, and these in turn correspond to one undissected 10-gon + five ways to divide a 10-gon into two 6-gons. a(10)=12 corresponds to (9,1,1)=9 and (9,2,4)=4,5, corresponding to one undissected 11-gon + the eleven ways to divide an 11-gon into a 6-gon and 7-gon. - Tom Copeland, Feb 15 2014 MATHEMATICA nmax=20; aa=ConstantArray[0, nmax]; aa[[1]]=0; Do[AGF=1+Sum[aa[[n]]*x^n, {n, 1, j-1}]+koef*x^j; sol=Solve[Coefficient[1-(1+x)*AGF+x*AGF^2 +x^4*AGF^5, x, j]==0, koef][[1]]; aa[[j]]=koef/.sol[[1]], {j, 2, nmax}]; Flatten[{1, aa}] (* Vaclav Kotesovec, Mar 23 2014 *) PROG (PARI) N=66; Vec(serreverse(x*(1-x^3*sum(k=1, N, x^k))+O(x^N))) CROSSREFS Cf. A001003 (rev. of x*(1-1*sum(k>=1,x^k)) ), A046736 (rev. of x*(1-x*sum(k>=1,x^k)) ), A054514 (rev. of x*(1-x^2*sum(k>=1,x^k)) ). Cf. A000108 (rev. of x/(1+1*sum(k>=1,x^k)) ), A005043 (rev. of x/(1+x*sum(k>=1,x^k)) ), A114997 (rev. of x/(1+x^2*sum(k>=1,x^k)) ), A215341 (rev. of x/(1+x^3*sum(k>=1,x^k)) ). Sequence in context: A081846 A078816 A051936 * A146923 A256977 A087883 Adjacent sequences:  A215339 A215340 A215341 * A215343 A215344 A215345 KEYWORD nonn AUTHOR Joerg Arndt, Aug 19 2012 STATUS approved

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Last modified October 22 19:53 EDT 2019. Contains 328319 sequences. (Running on oeis4.)