OFFSET
1,1
FORMULA
a(n)= (sqrt(7)-1)^degree(cyclotomic(n,x),x)*cyclotomic(n,(4+sqrt(7)/3) L(n)=6*F(n-1)+F(n+1) F(2n)=Product(d|2n) a(d), F(2n+1)=Product(d|2n+1) a(2d). L(2n+1)=Product(d|2n+1, a(d)), for k>0: L(2^k*(2n+1))=Product(d|2n+1, a(2^(k+1)*d)). for odd prime p, a(p)=L(p)/2, a(2p)=f(p) a(1)=2, a(2)=1; a(2^(k+1))=L(2^k);
EXAMPLE
F(12)=a(1)*a(2)*a(3)*a(4)*a(6)*a(12)=2*1*22*16*10*148=1041920
F(9)=a(2)*a(6)*a(18)= 1*10*2152=21520
L(12)=a(8)*a(24)=184*29968=5514112
L(21)=a(1)*a(3)*a(7)*a(21)=2*22*4264*3343936=627375896576
MAPLE
with(numtheory): a[1]:=2:a[2]:=1:for n from 3 to 60 do a[n]:=round(evalf((sqrt(7)-1)^degree(cyclotomic(n, x), x) *cyclotomic(n, (4+sqrt(7))/3), 30)) od: seq(a[n], n=1..60);
CROSSREFS
KEYWORD
nonn
AUTHOR
Miklos Kristof, Apr 03 2007
STATUS
approved