OFFSET
0,3
COMMENTS
[x^n] (1+x)^(1/2^n) denotes the coefficient of x^n in the (2^n)-root of (1+x), which has a denominator equal to 2^[n(n+1) - A000120(n)].
EXAMPLE
This sequence forms the numerators of coefficients [x^n] (1+x)^(1/2^n),
where the denominators equal 2^b(n) and b(n) takes on values:
[0,1,5,10,19,28,40,53,71,88,108,129,154,179,207,236,271,304,...],
which is described by b(n) = n(n+1) - A000120(n) for n>=0.
PROG
(PARI) {a(n)=polcoeff((1+x+x*O(x^n))^(1/2^n), n)*2^(n*(n+1)-subst(Pol(binary(n)), x, 1))}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Oct 26 2007
STATUS
approved