OFFSET
0,7
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Dominique BĂ©nard, Orientable imbedding of line graphs, J. Combinatorial Theory Ser. B 24 (1978), no. 1, 34--43. MR0485482(58 #5312)
Index entries for linear recurrences with constant coefficients, signature (3,-3,1,1,-3,3,-1).
FORMULA
G.f.: (1-2*x+2*x^3-2*x^4+3*x^5)/((1+x+x^2+x^3)*(1-x)^4). [Bruno Berselli, May 26 2012]
a(n) = 1+(2*(n-5)*(n-1)*n-3*(1+(-1)^n)*(1-i^((n-1)*n)))/24, where i=sqrt(-1). [Bruno Berselli, May 26 2012]
MATHEMATICA
Table[Floor[(n + 1) (n - 3) ((n - 4)/12)], {n, 0, 60}] (* Bruno Berselli, May 26 2012 *)
PROG
(Magma) m:=61; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!((1-2*x+2*x^3-2*x^4+3*x^5)/((1+x+x^2+x^3)*(1-x)^4))); // Bruno Berselli, May 26 2012
(Maxima) makelist(1+(2*(n-5)*(n-1)*n-3*(1+(-1)^n)*(1-%i^((n-1)*n)))/24, n, 0, 60); /* Bruno Berselli, May 26 2012 */
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
N. J. A. Sloane, May 26 2012
STATUS
approved