OFFSET
0,4
COMMENTS
What is the correct name for the rational sequence c(n) = 1, -1/2, 0, -1/4, 0, 1/2, 0, -17/8, 0, 31/2, 0, ... (a variant of the second fractional Euler numbers)?
Its binomial transform is f(n) = 1, 1/2, 0, -3/4, -2, -7/2, -4, -23/8, -6, -45/2, -8, 655/4, -10, ... = a(n)/A006519(n+1).
FORMULA
By definition f(0) - c(0), f(1) + c(1), f(2) - c(2), f(3) + c(3), ... is an autosequence of the first kind, here 1 - 1 = 0, 1/2 - 1/2 = 0, 0 - 0 = 0, -3/4 - 1/4 = -1, -2 - 0 = -2, -7/2 + 1/2 = -3, ... i.e., t(n) = 0, 0, followed by -A001477(n), not in the OEIS, but the corresponding autosequence of the second kind is: A199969 = 0, 0, -2, -3, -4, ... Hence f(n) from c(n) and t(n).
MAPLE
A198631 := proc(n)
1/(1+exp(-x)) ;
coeftayl(%, x=0, n) ;
numer(%*n!) ;
end proc:
A006519 := proc(n)
2^padic[ordp](n, 2) ;
end proc:
subsop(2=-1/2, L) ;
b := BINOMIAL(%) ;
for i from 1 to nops(b) do
printf("%d, ", numer(b[i])) ;
end do: # R. J. Mathar, Feb 21 2017
CROSSREFS
KEYWORD
sign
AUTHOR
Paul Curtz, Jan 31 2017
STATUS
approved