OFFSET
1,2
FORMULA
a(n+1)/a(n) = A027375(n+1).
a(n) = (1/2)*Product_{k=1..n} Sum_{d|k} moebius(d)*2^(k/d).
a(n) ~ c * 2^(n*(n+1)/2), where c = 0.09412540696949274854160062245002977344042957885767746756023904566838799439... - Vaclav Kotesovec, Apr 19 2024
MATHEMATICA
b[n_] := DivisorSum[n, MoebiusMu[n/#]*2^#& ]; a[n_] := a[n] = If[n == 1, 1, a[n-1]*b[n]]; Array[a, 18] (* Jean-François Alcover, Dec 18 2015 *)
Table[Det[Table[GCD[2^i-1, 2^j-1], {i, n}, {j, n}]], {n, 20}] (* Harvey P. Dale, Sep 23 2022 *)
PROG
(PARI) a(n)=if(n<1, 0, (1/2)*prod(k=1, n, sumdiv(k, d, moebius(d)*2^(k/d))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 03 2013
STATUS
approved