an amusing sequence from Belgium!

[N. J. A. Sloane]

Someone asked me this morning to explain the sequence

1, 2, 6, 21, 85, 430, 2586, ...

It combines two of my interests, sequences
and error-correction!

Based on my answer, I added this to the OEIS:

%I A090805
%S A090805 1,2,6,21,85,430,2586,18109,144880
%N A090805 A simple recurrence with one error.
%C A090805 I included this in the OEIS only because was published on a web page. The explanation is my own - perhaps the original proposer had a different explanation.
%D A090805 Found on a puzzle page.
%H A090805 Hugo Delestinne, <a href="http://users.skynet.be/lch/mquiz/mquiz%202003/vragen/mquiz_2003_tafelronde_2.htm">Meerdaelquiz</a>
%F A090805 a(0) = 1; a(n) = n*(a(n-1) + 1) but make an error if n = 4.
%e A090805 1..add.1..multiply.by 1 -> 2
%e A090805 2..add.1..multiply.by 2 -> 6
%e A090805 6......1............. 3 -> 21
%e A090805 21.....1............. 4 -> 88 but now you make a mistake and write 85
%e A090805 85.....1............. 5 -> 430
%e A090805 430....1............. 6 -> 2586
%e A090805 etc
%K A090805 nonn,easy,more,new,dumb
%O A090805 0,2
%A A090805 njas, Feb 12 2004

Any Flemish- (or Dutch-) speaking seqfans might enjoy
the other puzzles on that page.

NJAS

By the way, I am NOT interested in getting
any more sequences like this....