A393301 a(1) = 0; for n > 1, a(n) is the smallest unused number k such that k! contains the concatenation of a(1), a(2), ..., a(n-1) as a substring.

0, 5, 18, 87, 311, 11249

Offset

1,2

Links

Table of n, a(n) for n=1..6.

Formula

a(n) > a(n-1).

Example

a(4) = 87 as 87! = 2107757...000000 (133 digits) which contains a(1)|a(2)|a(3) = '0518' as a substring.

Crossrefs

Cf. A000142, A393300, A385673, A346120, A392010, A392011.

Sequence in context: A199257 A188206 A156305 * A369362 A213190 A151490

Adjacent sequences: A393298 A393299 A393300 * A393302 A393303 A393304

Keyword

nonn,base,hard,more

Author

Scott R. Shannon, Feb 10 2026

Status

approved