OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,2,-2,0,0,-1,1).
FORMULA
G.f.: x*(x^8 - 5*x^4 - x^3 - x^2 - x - 1) / ((x-1)^3*(x+1)^2*(x^2+1)^2). - Colin Barker, Dec 13 2012
EXAMPLE
a(5)=11 because 11 is the largest number k such that the equation 6*x_1 + 7*x_2 + 8*x_3 + 9*x_4 + 10*x_5 = k has no solution for any nonnegative x_i (in other words, for every k > 11 there exist one or more solutions).
MATHEMATICA
Table[FrobeniusNumber[{n + 1, n + 2, n + 3, n + 4}], {n, 1, 100}]
Table[(Floor[(n-1)/4]+1)*(n+1)-1, {n, 57}] (* Zak Seidov, Jan 10 2015 *)
FrobeniusNumber/@Partition[Range[2, 70], 5, 1] (* or *) LinearRecurrence[ {1, 0, 0, 2, -2, 0, 0, -1, 1}, {1, 2, 3, 4, 11, 13, 15, 17, 29}, 70] (* Harvey P. Dale, Oct 07 2016 *)
PROG
(PARI)for (n=1, 57, print1((floor((n-1)/4)+1)*(n+1)-1 ", "))\\ Zak Seidov, Jan 10 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Artur Jasinski, Apr 05 2008
STATUS
approved