A171658 Primes ending with the digits 21 which are the only primes in their century.

155921, 5649221, 6726821, 8598221, 8825321, 9953621, 10303721, 11948021, 12117121, 14645921, 14821721, 14866421, 15275021, 17270621, 17524921, 18497321, 19193921, 19731821, 20741621, 21721621, 22170221, 23009521, 24257921, 24579221, 24919721

Offset

1,1

Comments

Primes of the form 100*k+21 with no other prime of the form 100*k+j for j=1 to 99 with the same k.

Thanks for the assistance and research of John Moyer. There is likely an infinite number of such primes.

Links

Table of n, a(n) for n=1..25.

Example

a(1)=155921 is prime and it is the only prime between 155900 and 156000.

Crossrefs

Cf. A164987.

Sequence in context: A049443 A228473 A156118 * A347936 A347939 A177811

Adjacent sequences: A171655 A171656 A171657 * A171659 A171660 A171661

Keyword

nonn,base

Author

Ki Punches, Dec 14 2009

Extensions

Definition detailed and more terms appended by R. J. Mathar, Oct 09 2010

Status

approved