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A052080
Concatenation of n consecutive descending numbers starting from a(n) produces the smallest possible prime of this form, 0 if no such prime exists.
3
2, 4, 0, 10, 7, 0, 73, 46, 0, 56, 219, 0, 25, 60, 0, 52, 117, 0, 535, 172, 0
OFFSET
1,1
COMMENTS
First hard cases occur for n = 22, 88 and 110.
a(22) = 10^1631 + 10 was found by James G. Merickel in Feb 2011.
a(88) = 10^14 + 6.
a(110) = 10^19 + 26 was found by Chris Nash.
EXAMPLE
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.
CROSSREFS
KEYWORD
nonn,base,hard
AUTHOR
Patrick De Geest, Jan 15 2000
EXTENSIONS
Terms a(7)-a(21) calculated by Carlos Rivera and Felice Russo
STATUS
approved