OFFSET
1,3
COMMENTS
a(9) = 2299131884087642202247291403507120751687796592498104258 * C, where C is a composite factor with 96 digits.
C = P47*P49, with P47 = 88967307877356450624418823383132738084943851019 and
P49 = 4512180962860489443011495305279720577473472225641. - Hugo Pfoertner, Jan 09 2021
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..11
FORMULA
a(n) = (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n for n >= 3. - Andrew Howroyd, Jan 09 2021
MAPLE
seq(A340312_row(n)[2^(n-1)+1], n = 1..8);
PROG
(PARI) a(n) = {if(n<=2, n==1, (2*binomial(2^n-1, 2^(n-1)) + (2^n-1)*binomial(2^(n-1), 2^(n-2)))/2^n)} \\ Andrew Howroyd, Jan 09 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Jan 06 2021
STATUS
approved