A062221 Numbers k such that the smoothly undulating palindromic number (72*10^k - 27)/99 is a prime.

3, 5, 9, 17, 71, 99, 243, 7595, 9273, 53847

Offset: 1

Author

Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001

Keywords

• nonn
• base
• more

Comments

Prime versus probable prime status and proofs are given in the author's table.

No further terms < 100000. - Ray Chandler, Aug 17 2011

Examples

			k=17 -> (72*10^17 - 27)/99 = 72727272727272727.
		

Links

• Patrick De Geest, SUPP Reference Table - 727
• Index entries for sequences related to smoothly undulating palindromic primes

Crossrefs

Cf. A062209-A062232, A059758, A032758.

Extensions

a(10)=53847 from Patrick De Geest, Aug 06 2004

Edited by Ray Chandler, Aug 17 2011