A260642 Numbers in A004782, n-1 | C(n-1), but not in A081767, n-1 | C(n), where C(n) = A000108(n) = 2n!/n!(n+1)! are the Catalan numbers.

3, 7, 127, 511, 4095, 8191, 131071, 8388607, 33554431, 67108863, 2147483647, 8589934591, 137438953471, 2199023255551, 17592186044415, 35184372088831, 70368744177663, 281474976710655, 562949953421311, 36028797018963967, 72057594037927935

Offset: 1

Author

M. F. Hasler, Nov 11 2015

Keywords

• nonn

Comments

It appears that all terms are of the form 2^k-1 ; see A260641 for the k-values.

Crossrefs

Cf. A000108, A260641, A004782, A081767, A014847.

Formula

a(n) = 2^A260641(n)-1 = A000225(A260641(n)), i.e., equals A000225 o A260641.

Equals A004782 \ A081767.