OFFSET
1,2
COMMENTS
EXAMPLE
MATHEMATICA
nmax = 40;
pell = {1, 2};
pp = {1, 2};
Do[s = 2*pell[[-1]] + pell[[-2]];
AppendTo[pell, s];
AppendTo[pp, s/Times @@ pp[[Most[Divisors[n]]]]], {n, 3, nmax}];
a[2] = 2;
a[n_] := pp[[n]]/GCD[pp[[n]], n];
PROG
(PARI) T(n) = ([2, 1; 1, 0]^n)[2, 1]
b(n) = my(v=divisors(n)); prod(i=1, #v, T(v[i])^moebius(n/v[i]))
a(n) = if(n==2, 2, b(n)/gcd(n, b(n)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jianing Song, Jul 02 2019
STATUS
approved