2,3
Odd Catalan number is A038003[n] = A000108[2^n-1] = binomial(2^(n+1)-2, 2^n-1)/(2^n).
Table of n, a(n) for n=2..15.
There is no a(1) because A038003[1] = 1.
a(2) = 1 because A038003[2] = 5 squarefree.
a(3) = 1 because A038003[3] = 429 = 3*11*13 squarefree.
a(4) = 3 because A038003[4] = 9694845 = 3^2*5*17*19*23*29.
Cf. A038003, A000108.
Sequence in context: A135574 A008969 A199577 * A153257 A002185 A002589
Adjacent sequences: A119905 A119906 A119907 * A119909 A119910 A119911
nonn
Alexander Adamchuk, Aug 02 2006
approved
