A160952 a(n)=largest (n+1)-digit prime formed by appending a digit to a(n-1); a(0)=2.

2, 29, 293, 2939, 29399, 293999, 2939999, 29399999

Offset

0,1

Comments

There is no prime a(8) since 293999991 to 293999999 are all composite.

This is also one of five longest possible sequences of primes where each term is formed by appending a digit to the previous term. Alternatively, one can view 29399999 as a prime where truncating the last digit successively always produces a prime. These are called Right-truncatable primes and the other four with 8 digits are 23399339, 37337999, 5939339 and 73939133. A list of all 83 possible Right-truncatable primes can be found in links for A024770. I have independently verified that this list is complete.

Links

Table of n, a(n) for n=0..7.

Example

a(0)=2, a(1)=29, a(2)=293, a(3)=2939, a(4)=29399, a(5)=293999, a(6)=2939999, a(7)=29399999.

Crossrefs

Cf. A024770, A000040.

Sequence in context: A077023 A352065 A101750 * A088615 A091716 A198698

Adjacent sequences: A160949 A160950 A160951 * A160953 A160954 A160955

Keyword

base,fini,full,nonn,uned

Author

Vladislav-Stepan Malakhovsky and Juri-Stepan Gerasimov, May 31 2009

Extensions

Syntactically incorrect maple code deleted by R. J. Mathar, Oct 15 2011

Status

approved