OFFSET
2,2
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Andrew Howroyd, Table of n, a(n) for n = 2..1000
T. R. S. Walsh and A. B. Lehman, Counting rooted maps by genus. III: Nonseparable maps, J. Combinatorial Theory Ser. B 18 (1975), 222-259.
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
FORMULA
From Colin Barker, Apr 08 2013: (Start)
a(n) = (2160+846*n-1027*n^2-345*n^3+125*n^4+39*n^5+2*n^6)/360.
G.f.: -x^2*(5*x^6-29*x^5+65*x^4-63*x^3+12*x^2+13*x+1) / (x-1)^7. (End)
E.g.f.: exp(x)*(2160 - 360*x - 540*x^2 + 1560*x^3 + 645*x^4 + 69*x^5 + 2*x^6)/360 - 6 - 5*x. - Stefano Spezia, Jul 18 2024
PROG
(PARI) a(n)={if(n<2, 0, (2*n^6 + 39*n^5 + 125*n^4 - 345*n^3 - 1027*n^2 + 846*n + 2160)/360)} \\ Andrew Howroyd, Apr 01 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Title improved by Sean A. Irvine, Apr 03 2017
Terms a(14) and beyond from Andrew Howroyd, Apr 01 2021
STATUS
approved