OFFSET
1,1
COMMENTS
Sunlet graphs are defined for n>=3; extended to n=1 using closed form.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Molecular Topological Index
Eric Weisstein's World of Mathematics, Sun Graph
Index entries for linear recurrences with constant coefficients, signature (2,1,-4,1,2,-1).
FORMULA
a(n) = n*(2*n*(n+3)+(-1)^n+7).
G.f.: 2*x*(x^4+2*x^3+14*x+7)/((x-1)^4*(x+1)^2). - Colin Barker, Aug 07 2012
E.g.f.: x*((15 + 12*x + 2*x^2)*exp(x) - exp(-x)). - G. C. Greubel, Jan 05 2019
MATHEMATICA
Table[n*(2*n*(n+3)+(-1)^n+7), {n, 1, 40}] (* G. C. Greubel, Jan 05 2019 *)
PROG
(PARI) vector(40, n, n*(2*n*(n+3)+(-1)^n+7)) \\ G. C. Greubel, Jan 05 2019
(Magma) [n*(2*n*(n+3)+(-1)^n+7): n in [1..40]]; // G. C. Greubel, Jan 05 2019
(Sage) [n*(2*n*(n+3)+(-1)^n+7) for n in (1..40)] # G. C. Greubel, Jan 05 2019
(GAP) List([1..40], n -> n*(2*n*(n+3)+(-1)^n+7)); # G. C. Greubel, Jan 05 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Jul 11 2011
STATUS
approved