OFFSET
0,3
COMMENTS
The generating function can be arranged to have four zeros at the fourth roots of unity. - Jaume Oliver Lafont, Mar 23 2009
Also, the arithmetic function uhat(n,4,3) as defined in A291041. - Robert Price, Aug 25 2017
Decimal expansion of 1111/90000. - Elmo R. Oliveira, May 06 2024
LINKS
Eric Weisstein's World of Mathematics, Four-Color Theorem
Wikipedia, Four color theorem
Index entries for linear recurrences with constant coefficients, signature (1).
FORMULA
G.f.: x*(1+x+x^2+x^3)/(1-x).
G.f.: x*(1-x^4)/(1-x)^2. - Jaume Oliver Lafont, Mar 20 2009
G.f.: Product_{k=0..3} (1-I^k*x)*x/(1-x)^2. - Jaume Oliver Lafont, Mar 23 2009
a(n) = min(n,4). - Wesley Ivan Hurt, Apr 16 2014
E.g.f.: 4*exp(x) - 4 - 3*x - x^2 - x^3/6. - Stefano Spezia, May 19 2024
MATHEMATICA
PadRight[Range[0, 3], 100, 4] (* Paolo Xausa, Aug 22 2024 *)
PROG
(PARI) a(n)=if(n<4, n, 4)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jaume Oliver Lafont, Mar 18 2009
STATUS
approved