2,1

A038003[n] = Binomial(2^(n+1)-2, 2^n-1)/(2^n).

a(2) = 5 because A038003[2] = 5.

a(3) = 3 because A038003[3] = 429 = 3*11*13.

Cf. A038003, A000108.

Sequence in context: A010038 A056597 A019624 this_sequence A021656 A084538 A079799

Adjacent sequences: A120272 A120273 A120274 this_sequence A120276 A120277 A120278

nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Jul 04 2006