A100769 Beginning with 1, least positive integer not occurring earlier such that the n-th partial concatenation is a multiple of n.

1, 2, 3, 6, 5, 4, 16, 8, 9, 10, 14, 12, 20, 26, 35, 36, 37, 44, 7, 40, 31, 22, 19, 28, 25, 32, 39, 56, 60, 70, 43, 52, 49, 30, 15, 48, 51, 58, 59, 120, 50, 64, 93, 88, 65, 86, 61, 168, 101, 100, 57, 68, 13, 84, 155, 104, 158, 54, 127, 80, 133, 38, 78, 144, 45, 138, 18, 76

Offset

1,2

Links

Paul Tek, Table of n, a(n) for n = 1..10000

Paul Tek, PARI program for this sequence

Example

a(7) = 16 as the concatenation 12365416 of first seven terms is a multiple of 7. No number less than 16 and more than 6 fits in.

Mathematica

a[1] = 1; a[n_] := a[n] = Block[{t = 1}, While[Mod[FromDigits@ Flatten[IntegerDigits /@ Join[Array[a, n - 1], {t}]], n] != 0 || MemberQ[Array[a, n - 1], t], t++]; t]; Array[a, 68] (* Giorgos Kalogeropoulos, May 07 2023 *)

Prog

(PARI) See Link section.

Crossrefs

Cf. A099552, A100770.

Sequence in context: A269373 A269374 A137761 * A353977 A023889 A327669

Adjacent sequences: A100766 A100767 A100768 * A100770 A100771 A100772

Keyword

base,easy,nonn

Author

Amarnath Murthy, Nov 27 2004

Extensions

More terms from Joshua Zucker, May 27 2005

Status

approved