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A365692
G.f. A(x) satisfies A(x) = 1 + x*A(x) / (1 - x^2*A(x)^4).
2
1, 1, 1, 2, 7, 23, 72, 238, 831, 2959, 10645, 38824, 143492, 535700, 2016020, 7641574, 29152015, 111841263, 431209723, 1669945778, 6493144143, 25338440143, 99204579648, 389570145288, 1534026813892, 6055885764548, 23962654178012, 95023123291680
OFFSET
0,4
FORMULA
a(n) = Sum_{k=0..floor(n/2)} binomial(n-k-1,k) * binomial(n+2*k+1,n-2*k) / (n+2*k+1).
D-finite with recurrence of order 16 (see link). - Robert Israel, May 18 2026
PROG
(PARI) a(n) = sum(k=0, n\2, binomial(n-k-1, k)*binomial(n+2*k+1, n-2*k)/(n+2*k+1));
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Seiichi Manyama, Sep 16 2023
STATUS
approved