OFFSET
1,2
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
From Colin Barker, Dec 14 2015: (Start)
a(n) = (3/2+(3*i)/2)*(i^n-i*(-i)^n)-(-1)^n+6*(n+1)-9 where i = sqrt(-1).
a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.
G.f.: x*(1+4*x+14*x^2+4*x^3+x^4) / ((1-x)^2*(1+x)*(1+x^2)).
(End)
PROG
(PARI) for (x=1, 200, for (y=1, 200, if (kronecker(x, y)==moebius(gcd(x, y)), write("km.txt", x, "; ", y, " : ", kronecker(x, y)))))
(PARI) isok(n) = kronecker(6, n) == moebius(gcd(6, n)); \\ Michel Marcus, Mar 17 2014
(PARI) Vec(x*(1+4*x+14*x^2+4*x^3+x^4)/((1-x)^2*(1+x)*(1+x^2)) + O(x^100)) \\ Colin Barker, Dec 14 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jon Perry, Sep 17 2002
EXTENSIONS
More terms from Michel Marcus, Mar 17 2014
STATUS
approved