%I #15 May 13 2023 01:47:23
%S 3,5,35,139,153,253,1053,2015,3703,6933,8173,11959
%N Numbers k such that the concatenation of n successive descending digits (1,0,9,8,7,...) starting with 1 is prime.
%C Digits are in descending order beginning with 1 and after 0 comes 9.
%C Terms must end in 3, 5 or 9. - _Michael S. Branicky_, May 11 2023
%e 5 is a term since 10987 is a prime.
%p filter:= proc(n) local i; isprime( add(10^(n-1-i)*(1-i mod 10), i=0..n-1)) end proc:
%p select(filter, [$1..4000]); # _Robert Israel_, Mar 08 2023
%t fQ[n_] := PrimeQ@ FromDigits@ Mod[2-Range@n, 10]; lst = {}; Do[ If[fQ@n, AppendTo[lst, n]; Print@n], {n, 6000}]; lst
%Y Cf. A120804, A120819, A120829.
%K nonn,base,hard,more
%O 1,1
%A _Robert G. Wilson v_, Jul 05 2006
%E Name corrected by _Robert Israel_, Mar 08 2023
%E a(10)-a(12) from _Michael S. Branicky_, May 11 2023