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A176024
Numbers k such that the reverse concatenation of the first k integers (A000422(k)) is a prime.
4
OFFSET
1,1
COMMENTS
a(1) was pointed out by Artur Jasinski, Mar 30 2008 (see A000422).
a(2) was found by Eric W. Weisstein, Apr 06 2010.
a(3) > 84300. - Tyler Busby, Feb 21 2023
EXAMPLE
a(1) is 82 since the 155-digit number 828180...54321 is prime.
a(2) is 37765 since the 177719-digit number 377653776437763...54321 is (a probable) prime.
CROSSREFS
KEYWORD
nonn,hard,more,base,bref
AUTHOR
Eric W. Weisstein, Apr 06 2010
EXTENSIONS
Edited by N. J. A. Sloane, Dec 03 2021
STATUS
approved