A095247 Least k such that the concatenation a(1), a(2), a(3), ..., a(n-1), a(n) is divisible by n if and only if n is not a prime.

1, 1, 2, 4, 1, 6, 1, 6, 5, 10, 1, 16, 1, 6, 5, 12, 1, 2, 1, 20, 12, 10, 1, 28, 25, 4, 25, 36, 1, 20, 1, 28, 25, 6, 5, 40, 1, 30, 5, 20, 1, 36, 1, 36, 5, 26, 1, 12, 8, 50, 53, 16, 1, 22, 45, 52, 5, 16, 1, 40, 1, 32, 69, 12, 65, 58, 1, 52, 22, 40, 1, 28, 1, 24, 50, 44, 59, 38, 1, 60, 65, 70, 1

Offset

1,3

Comments

Contribution from Hagen von Eitzen, Oct 03 2009: (Start)

a(n) < n + 10^floor(log_2(n)).

If k >= 1 and n in {10^k, 2*10^k, 5*10^k} then a(n) = n.

If n is prime then a(n) in {1, 2}. (End)

Links

Table of n, a(n) for n=1..83.

Example

3 does not divide 112 while 4 divides 1124.

Crossrefs

Sequence in context: A125847 A078886 A307796 * A007734 A171233 A362004

Adjacent sequences: A095244 A095245 A095246 * A095248 A095249 A095250

Keyword

base,nonn,uned

Author

Amarnath Murthy, Jun 17 2004

Extensions

More terms from Hagen von Eitzen, Oct 03 2009

Status

approved