OFFSET
0,1
COMMENTS
REFERENCES
S. Humphries, Charged particle beams. J. Wiley, N.Y. 1990.
M. Reiser, Theory and design of charged particle beams. J. Wiley, N.Y. 1994.
FORMULA
a(n) = numerator(sum(k=1..n, 4^(-k)*binomial(2*k,k)*sum(j=1..k, (j!*binomial(k,j)*(-1)^(j)*Stirling1(n+j,j))/(n+j)!))), n>0, a(0)=2. - Vladimir Kruchinin, Feb 18 2015
a(n) = numerator(Sum_{k=0..n} binomial(1/2-n, k)*binomial(2*n-1/2, n-k)*Stirling2(n+k, k)*k!/((1-2*n)*(n+k)!)), n>0, a(0)=2. - Tani Akinari, Nov 05 2024
EXAMPLE
Series expansion is sqrt(x-1)*(2 + 1/6 (x-1) - 7/240 (x-1)^2 + 5/448 (x-1)^3 -...), hence a(0)=2, a(1)=1, a(2)=-7, a(3)=5, etc.
MATHEMATICA
a[n_] := If [n == 0, 2, Sum[4^(-k)*Binomial[2*k, k]*Sum[(j!*Binomial[k, j]*(-1)^j* StirlingS1[n+j, j])/(n+j)!, {j, 1, k}], {k, 1, n}]] // Numerator; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Feb 18 2015, after Vladimir Kruchinin *)
PROG
(Maxima)
a(n):=if n=0 then 2 else num(sum(4^(-k)*binomial(2*k, k)*sum((j!*binomial(k, j)*(-1)^(j)*stirling1(n+j, j))/(n+j)!, j, 1, k), k, 1, n)); /* Vladimir Kruchinin, Feb 18 2015 */
(Maxima) a(n):=if n=0 then 2 else num(sum(binomial(1/2-n, k)*binomial(2*n-1/2, n-k)*stirling2(n+k, k)*k!/((1-2*n)*(n+k)!), k, 0, n)); /* Tani Akinari, Nov 05 2024 */
CROSSREFS
KEYWORD
sign,frac,changed
AUTHOR
Zak Seidov, Oct 31 2002
STATUS
approved