A077189 Smallest concatenation 123...(k-1) k (k-1)...321 (a concatenation of natural numbers from 1 to k and back to 1) that is a multiple of 2n-1, or 0 if no such number exists.

1, 12321, 0, 12345654321, 12321, 121, 12345654321, 0

Offset

1,2

Comments

a(5k+3) = 0. Are there any other values of n such that a(n) = 0?

The next value, 2n-1 = 17, has k = 109, for a total of 435 digits and is too large to include. - Franklin T. Adams-Watters, Jun 02 2006

Links

Jinyuan Wang, Table of n, a(n) for n = 1..11

Example

a(5) = 12321 is a multiple of 9.

Crossrefs

Cf. A077180, A077181, A077182, A077183, A077184, A077186, A077188, A077190.

Cf. A120008.

Sequence in context: A250856 A242716 A077186 * A277947 A321492 A237782

Adjacent sequences: A077186 A077187 A077188 * A077190 A077191 A077192

Keyword

nonn,base

Author

Amarnath Murthy, Nov 01 2002

Extensions

More terms from Franklin T. Adams-Watters, Jun 02 2006

Status

approved