OFFSET
1,1
COMMENTS
Sequence contains numbers of form (21+60k), (39+60k), (42+60k), (48+60k), with k>=0.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).
FORMULA
G.f.: x*(12*x^4+6*x^3+3*x^2+18*x+21) / (x^5-x^4-x+1). - Colin Barker, Jun 16 2013
a(n) = (-3/4+(3*i)/4)*((1+i)*(-1)^n + (5+2*i)*(-i)^n + (2+5*i)*i^n - (10+10*i)*n) where i=sqrt(-1). - Colin Barker, Oct 16 2015
MATHEMATICA
LinearRecurrence[{1, 0, 0, 1, -1}, {21, 39, 42, 48, 81}, 60] (* Harvey P. Dale, Aug 28 2017 *)
PROG
(PARI) a(n) = (-3/4+(3*I)/4)*((1+I)*(-1)^n + (5+2*I)*(-I)^n + (2+5*I)*I^n - (10+10*I)*n) \\ Colin Barker, Oct 16 2015
(PARI) Vec(x*(12*x^4+6*x^3+3*x^2+18*x+21)/(x^5-x^4-x+1) + O(x^100)) \\ Colin Barker, Oct 16 2015
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Benoit Cloitre, Aug 07 2002
STATUS
approved