

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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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.


LINKS

Table of n, a(n) for n=1..21.
C. Rivera, Prime Puzzle 78


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

Cf. A052077, A052078, A052079.
Sequence in context: A021419 A180192 A066529 * A261754 A073451 A078022
Adjacent sequences: A052077 A052078 A052079 * A052081 A052082 A052083


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



