OFFSET
0,3
COMMENTS
Self-convolution inverse is A117210.
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: A(x) = exp( -Sum_{n>=1} A117212(n)*x^n/n ).
G.f.: A(x) = product_{k>=1}(1 + x^k)^(-mu(k)) where mu(k) is the Möbius function, A008683. - Stuart Clary, Apr 15 2006
MATHEMATICA
nmax = 88; CoefficientList[ Series[ Product[ (1 + x^k)^(-MoebiusMu[k]), {k, 1, nmax} ], {x, 0, nmax} ], x ] (* Stuart Clary, Apr 15 2006 *)
PROG
(PARI) {a(n)=if(n==0, 1, if(n==1, -1, (-1)^n-polcoeff(prod(i=1, n, sum(k=0, min(n\i, n-1), a(k)*x^(i*k))+x*O(x^n)), n, x)))}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Mar 03 2006
STATUS
approved