A089778 a(n) is the n-th prime that ends with prime(n), or 0 if there do not exist n primes ending with prime(n).

2, 13, 0, 47, 911, 1213, 2417, 1619, 1723, 2729, 2131, 3137, 4241, 4643, 3947, 4153, 4759, 5861, 4967, 6271, 6173, 6379, 6883, 7589, 7297, 98101, 97103, 104107, 108109, 129113, 130127, 122131, 174137, 136139, 131149, 150151, 172157, 147163

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(5) = 911 because prime(5) = 11 and the first 5 primes ending with 11 are 11, 211, 311, 811 and 911.
a(3) = 0 because prime(3) = 5 and only 1 prime ends with 5.

Maple

f:= proc(n) local p, d, k, count;
p:= ithprime(n);
d:= 10^(ilog10(p)+1);
count:= 1;
for k from 1 while count < n do
   if isprime(k*d+p) then count:= count+1 fi
od;
(k-1)*d+p
end proc:
f(3):= 0:
map(f, [$1..100]); # Robert Israel, Dec 10 2017

Prog

(PARI) a(n) = if(n == 3, return(0)); my(p = prime(n), d = 10^(logint(p, 10)+1), i = 1); for(x=0, +oo, if(isprime(x*d+p), i++; if(i > n, return(x*d+p)))); \\ Iain Fox, Dec 10 2017

Crossrefs

Sequence in context: A130769 A128033 A090954 * A088253 A249224 A217010

Adjacent sequences: A089775 A089776 A089777 * A089779 A089780 A089781

Keyword

base,nonn,easy

Author

Amarnath Murthy, Nov 24 2003

Extensions

Corrected and extended by David Wasserman, Oct 12 2005

Status

approved