OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (2,-1,0,1,-2,1).
FORMULA
a(n) = Sum_{i=1..n} A047425(i).
From Wesley Ivan Hurt, Jun 04 2016: (Start)
G.f.: x*(3+x+x^2+x^3+2*x^4)/((1-x)^3*(1+x+x^2+x^3)).
a(n) = 2*a(n-1) - a(n-2) + a(n-4) - 2*a(n-5) + a(n-6) for n>6.
a(n) = (4*n^2+2*n+5-2*I^(-n)-2*I^n-I^(2*n))/4 where I=sqrt(-1). (End)
MAPLE
A171835:=n->(4*n^2+2*n+5-2*I^(-n)-2*I^n-I^(2*n))/4: seq(A171835(n), n=1..80); # Wesley Ivan Hurt, Jun 04 2016
MATHEMATICA
CoefficientList[Series[(3 + x + x^2 + x^3 + 2*x^4)/((1 - x)^3*(1 + x + x^2 + x^3)), {x, 0, 80}], x] (* Wesley Ivan Hurt, Jun 04 2016 *)
Table[(4*n^2 +2*n +5 -2*(1 +(-1)^n)*I^n -(-1)^n)/4, {n, 1, 100}] (* G. C. Greubel, Sep 04 2018 *)
PROG
(PARI) vector(100, n, (4*n^2 +2*n +5 -2*(1 +(-1)^n)*I^n -(-1)^n)/4) \\ G. C. Greubel, Sep 04 2018
(Magma) C<I> := ComplexField(); [Round((4*n^2 +2*n +5 -2*(1 +(-1)^n)*I^n -(-1)^n)/4): n in [1..100]]; // G. C. Greubel, Sep 04 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Dec 19 2009
STATUS
approved