OFFSET
0,1
REFERENCES
James Munkres, Topology, 2nd ed., Pearson, 2000.
LINKS
Richard Courant and Herbert Robbins, What Is Mathematics?, Oxford, 1941, pp. 258-259.
Eric Weisstein's World of Mathematics, Euler Characteristic
Index entries for linear recurrences with constant coefficients, signature (2,-1).
FORMULA
a(n) = 2 - 2*n.
G.f.: 2*(1-2*x)/(1-x)^2. - Vincenzo Librandi, Feb 01 2015
a(n) = 2*A022958(n+1). - R. J. Mathar, Oct 05 2017
E.g.f.: 2*exp(x)*(1 - x). - Stefano Spezia, Sep 10 2022
MAPLE
MATHEMATICA
Table[2 - 2 n, {n, 0, 100}] (* Wesley Ivan Hurt, Mar 15 2014 *)
LinearRecurrence[{2, -1}, {2, 0}, 80] (* Harvey P. Dale, Jan 31 2015 *)
CoefficientList[Series[2 (1-2 x) / (1 - x)^2, {x, 0, 60}], x] (* Vincenzo Librandi, Feb 01 2015 *)
PROG
(Magma) [2-2*n: n in [0..60]]; // Vincenzo Librandi, Feb 01 2015
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Eric M. Schmidt, Mar 12 2014
STATUS
approved