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

Author

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

Keywords

• base
• fini
• full
• nonn
• uned

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.

Examples

			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.

Extensions

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