OFFSET
2,4
COMMENTS
Genera of curves B whose function field K(B) is Galois closure [Galois closed, perhaps? - N. J. A. Sloane, Feb 08 2010].
a(n) is also the cyclomatic number of the (n-2)-transposition graph. - Eric W. Weisstein, Apr 03 2017
REFERENCES
Nils Bruin and Noam D. Elkies, Trinomials ax^7+bx+c and ax^8+bx+c with Galois Groups of Order 168 and 8*168, in Claus Fieker, David R. Kohel (Editors): Algorithmic Number Theory, 5th International Symposium, ANTS-V, Lecture Notes in Computer Science 2369 Springer 2002, pp. 172 - 188.
LINKS
G. C. Greubel, Table of n, a(n) for n = 2..445
Eric Weisstein's World of Mathematics, Cyclomatic Number
Eric Weisstein's World of Mathematics, Transposition Graph
FORMULA
E.g.f.: ( -4 +2*x +3*x^2 +4*(1-x)*exp(x) +2*(1-x^2)*log(1-x) )/(4*(1-x)). - G. C. Greubel, Feb 19 2021
MAPLE
MATHEMATICA
Table[(1/4)*(n^2 -5*n +2)*(n-2)! + 1, {n, 2, 30}]
PROG
(Sage) [(1/4)*(n^2 -5*n +2)*factorial(n-2) + 1 for n in (2..30)] # G. C. Greubel, Feb 19 2021
(Magma) [(1/4)*(n^2 -5*n +2)*Factorial(n-2) + 1: n in [2..30]]; // G. C. Greubel, Feb 19 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Feb 08 2010
STATUS
approved