A260642 - OEIS

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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.

1

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

(list; graph; refs; listen; history; text; internal format)

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