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
Examples
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.
Links
- Paul Tek, Table of n, a(n) for n = 1..10000
- Paul Tek, PARI program for this sequence
Programs
-
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 *) -
PARI
See Link section.
Extensions
More terms from Joshua Zucker, May 27 2005