OFFSET
0,2
COMMENTS
Euler transform of period 4 sequence [ -4,-4,-4,-3,...].
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
G.f.: Product_{n>0} (1-x^n)^4/(1-x^(4n)).
a(0) = 1, a(n) = -(4/n)*Sum_{k=1..n} A285895(k)*a(n-k) for n > 0. - Seiichi Manyama, Apr 29 2017
MAPLE
with(numtheory):
a:= proc(n) option remember; `if`(n=0, 1, add(add(d*
`if`(irem(d, 4)=0, -3, -4), d=divisors(j))*a(n-j), j=1..n)/n)
end:
seq(a(n), n=0..80); # Alois P. Heinz, Jan 07 2017
MATHEMATICA
CoefficientList[QPochhammer[x]^4/QPochhammer[x^4] + O[x]^80, x] (* Jean-François Alcover, Sep 19 2016 *)
PROG
(PARI) a(n)=if(n<0, 0, X=x+x*O(x^n); polcoeff(eta(X)^4/eta(X^4), n))
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, May 04 2003
STATUS
approved