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

1,1

Comments

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

Links

Table of n, a(n) for n=1..21.

Formula

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

Equals A004782 \ A081767.

Crossrefs

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

Sequence in context: A139159 A042329 A125956 * A128071 A079622 A182330

Adjacent sequences: A260639 A260640 A260641 * A260643 A260644 A260645

Keyword

nonn

Author

M. F. Hasler, Nov 11 2015

Status

approved