# [seqfan] Re: put the numbers from 1 to n such the sum of two of them are prime

N. J. A. Sloane njas at research.att.com
Tue Mar 15 17:32:43 CET 2011

```Peter, I admit I made a mistake in my definition of A187871.
Here is a corrected version  (in the internal format):

%I
%S 1,12,123,1234,14325,143256,1234765,12347658,123476589,11032567498
%N a(1)=1; for n > 1, a(n) is the smallest number that is formed by arranging the decimal numbers "1", "2", ..., "n" in some order so that the sum of every pair of adjacent numbers "i" "j" is prime.
%C A051237 and A187869 are the sequence that result if in addition we require that the number begins with "1" and ends with "n".
%H Claudio Meller, <a href="http://www.misacertijos.com.ar/2011/03/lineas-con-numeros-de-1-n.html">Lineas con numeros de 1 a n</a>.
%Y Cf. A051237, A187869.
%K nonn,base,more,changed
%O 1,2
%A N. J. A. Sloane (njas(AT)research.att.com), Mar 14 2011
%E a(6) to a(10) from Claudio Meller, Mar 14 2011

You sent a b-file for this. You version begins:

1,12,123,1234,14325,143256,1234765,12347658,123476589,12347658910,1234710985611,
123476512118910,12347651211891013,1234761310981112514,123476512118151491013,
12347651211891013161514,1234765891013161514171211,123476589101316151417121118

The difference is in the 10th term. Meller's term, 11032567498, is smaller
than your 12347658910, so yours is a different sequence. Can you tell
me exactly how you defined your version?

```