OFFSET
0,3
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,1,-1).
FORMULA
From Bruno Berselli, Jan 21 2016: (Start)
G.f.: (1 + x^2 + x^3 + 2*x^4 - x^5) / ((1 + x)*(1 - x)^2*(1 - x + x^2)*(1 + x + x^2)).
a(n) = a(n-1) + a(n-6) - a(n-7) for n>6.
a(n) = n - floor((n+1)/3) + ((-1)^n - (-1)^(floor(n/3)))/2 + 1. (End)
MATHEMATICA
RecurrenceTable[{a[0] == a[1] == 1, a[n] == Mod[a[n - 1], 4] + a[n - 2]}, a, {n, 70}]
Table[n - Floor[(n + 1)/3] + ((-1)^n - (-1)^Floor[n/3])/2 + 1, {n, 0, 70}] (* or *) LinearRecurrence[{1, 0, 0, 0, 0, 1, -1}, {1, 1, 2, 3, 5, 4, 5}, 80] (* Bruno Berselli, Jan 21 2016 *)
PROG
(PARI) a=vector(100); for(n=1, #a, if(n<3, a[n]=1, a[n]=a[n-1]%4+a[n-2])); a \\ Colin Barker, Jan 22 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
José María Grau Ribas, Jan 20 2016
EXTENSIONS
Edited by Bruno Berselli, Jan 21 2016.
STATUS
approved