OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..5000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).
FORMULA
a(n) = floor(ceiling((7n + 2)/2)/2).
a(n) = 2n-2-floor((n-1)/4). - Gary Detlefs, Mar 27 2010
From Colin Barker, Mar 13 2012: (Start)
a(n) = a(n-1)+a(n-4)-a(n-5) for n>5.
G.f.: x^2*(2+2*x+2*x^2+x^3)/((1-x)^2*(1+x)*(1+x^2)). (End)
From Wesley Ivan Hurt, May 21 2016: (Start)
a(n) = (14n-11+i^(2n)+(1-i)*i^(-n)+(1+i)*i^n)/8 where i=sqrt(-1).
MAPLE
MATHEMATICA
Select[Range[0, 100], MemberQ[{0, 2, 4, 6}, Mod[#, 7]]&] (* Vincenzo Librandi, Apr 26 2012 *)
LinearRecurrence[{1, 0, 0, 1, -1}, {0, 2, 4, 6, 7}, 80] (* Harvey P. Dale, Jun 21 2019 *)
PROG
(Magma) I:=[0, 2, 4, 6, 7]; [n le 5 select I[n] else Self(n-1)+Self(n-4)-Self(n-5): n in [1..70]]; // Vincenzo Librandi, Apr 26 2012
(PARI) A047293(n)=n*7\4-1 \\ M. F. Hasler, Apr 27 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved