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%I #22 Mar 04 2021 04:39:43
%S 2,4,0,10,7,0,73,46,0,56,219,0,25,60,0,52,117,0,535,172,0
%N Concatenation of n consecutive descending numbers starting from a(n) produces the smallest possible prime of this form, 0 if no such prime exists.
%C First hard cases occur for n = 22, 88 and 110.
%C a(22) = 10^1631 + 10 was found by _James G. Merickel_ in Feb 2011.
%C a(88) = 10^14 + 6.
%C a(110) = 10^19 + 26 was found by Chris Nash.
%H C. Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_078.htm">Prime Puzzle 78</a>
%e For n = 8 we have a(8) = 46 so the eight consecutive descending numbers 46,45,44,43,42,41,40 and 39 concatenated together gives the smallest possible prime of this form, 4645444342414039.
%Y Cf. A052077, A052078, A052079.
%K nonn,base,hard
%O 1,1
%A _Patrick De Geest_, Jan 15 2000
%E Terms a(7)-a(21) calculated by _Carlos Rivera_ and _Felice Russo_
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