A061111 a(1) = 1; a(n) = smallest number such that the concatenation a(1).0^*.a(2).0^*....0^*.a(n) is a perfect cube (where any number of 0's can be inserted between the terms).

1, 25, 9712, 8685582839, 70309163442200949867268191808152, 83387750596937905713672379983426538301395131506141618968183314995065134642469485779065066952875

Offset

1,2

Comments

The implication is that 10...01, 10...02, 10...03, ..., 10...024 are never cubes for any number of internal zeros, while 125 IS a cube, so a(2) = 25. - N. J. A. Sloane, Jul 21 2001

Links

Sean A. Irvine and Jon E. Schoenfield, Table of n, a(n) for n = 1..8

Amarnath Murthy, Exploring some new ideas on Smarandache type sets, functions and sequences, Smarandache Notions Journal Vol. 11, No. 1-2-3, Spring 2000, pp. 171-183.

Example

a(1) = 1, a(1).a(2) = 125 = 5^3, a(1).a(2).a(3) = 1259712 = 108^3, a(1).a(2).a(3).a(4) = 232679^3.

Crossrefs

Cf. A061109, A051671, A061110.

Sequence in context: A053860 A369582 A091744 * A238564 A195682 A082211

Adjacent sequences: A061108 A061109 A061110 * A061112 A061113 A061114

Keyword

base,nonn

Author

Amarnath Murthy, Apr 20 2001

Extensions

Offset and a(4) corrected and more terms from Sean A. Irvine, Jan 21 2023

Status

approved