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 A120333 Number of monocyclic skeletons with n carbon atoms and a ring size of 5. 3
 1, 1, 4, 9, 28, 71, 198, 521, 1418, 3773, 10153, 27114, 72705, 194531, 521447, 1397482, 3749836, 10067417, 27057233, 72779710, 195963184, 528127752, 1424707167, 3846943003, 10397057771, 28125235102, 76149287981, 206351312858, 559642013499, 1519019192097 (list; graph; refs; listen; history; text; internal format)
 OFFSET 5,3 REFERENCES Camden A. Parks and James B. Hendrickson, Enumeration of monocyclic and bicyclic carbon skeletons, J. Chem. Inf. Comput. Sci., vol. 31, 334-339 (1991). LINKS Andrew Howroyd, Table of n, a(n) for n = 5..200 EXAMPLE If n=10 then the number of monocyclic skeletons with ring size of five is 71. MATHEMATICA G[n_] := Module[{g}, Do[g[x_] = 1 + x*(g[x]^3/6 + g[x^2]*g[x]/2 + g[x^3]/3) + O[x]^n // Normal, {n}]; g[x]]; T[n_, k_] := Module[{t = G[n], g}, t = x*((t^2 + (t /. x -> x^2))/2); g[e_] = (Normal[t + O[x]^Quotient[n, e]] /. x -> x^e) + O[x]^n // Normal; Coefficient[(Sum[EulerPhi[d]*g[d]^(k/d), {d, Divisors[k]}]/k + If[OddQ[ k], g[1]*g[2]^Quotient[k, 2], (g[1]^2 + g[2])*g[2]^(k/2-1)/2])/2, x, n]]; a[n_] := T[n + 5, 5]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Jul 03 2018, after Andrew Howroyd *) CROSSREFS Column k=5 of A305059. Sequence in context: A101973 A244968 A071258 * A000368 A232765 A094255 Adjacent sequences:  A120330 A120331 A120332 * A120334 A120335 A120336 KEYWORD nonn AUTHOR Parthasarathy Nambi, Aug 13 2006 EXTENSIONS More terms from N. J. A. Sloane, Aug 27 2006 Terms a(26) and beyond from Andrew Howroyd, May 24 2018 STATUS approved

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Last modified July 17 02:50 EDT 2019. Contains 325092 sequences. (Running on oeis4.)