A192790 Molecular topological index of the Andrásfai graphs.

4, 80, 336, 880, 1820, 3264, 5320, 8096, 11700, 16240, 21824, 28560, 36556, 45920, 56760, 69184, 83300, 99216, 117040, 136880, 158844, 183040, 209576, 238560, 270100, 304304, 341280, 381136, 423980, 469920, 519064, 571520, 627396, 686800, 749840, 816624, 887260

Offset

1,1

Links

Table of n, a(n) for n=1..37.

Eric Weisstein's World of Mathematics, Andrásfai Graph.

Eric Weisstein's World of Mathematics, Molecular Topological Index.

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

Formula

a(n) = 2*n*(3*n-2)*(3*n-1).

a(n) = 4*A006566(n).

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4).

G.f.: 4*x*(1+16*x+10*x^2)/(x-1)^4. - R. J. Mathar, May 06 2014

E.g.f.: 2*x*(2 + 18*x + 9*x^2)*exp(x). - Elmo R. Oliveira, Aug 22 2025

Mathematica

LinearRecurrence[{4, -6, 4, -1}, {4, 80, 336, 880}, 30] (* Harvey P. Dale, Jan 31 2013 *)

Crossrefs

Cf. A006566.

Sequence in context: A381427 A125710 A204296 * A211152 A093854 A345459

Adjacent sequences: A192787 A192788 A192789 * A192791 A192792 A192793

Keyword

nonn,easy

Author

Eric W. Weisstein, Jul 10 2011

Extensions

More terms from Elmo R. Oliveira, Aug 22 2025

Status

approved