A096097 a(1) = 2, a(2) = 1; for n >= 3, a(n) = least prime not included earlier that divides the concatenation of all previous terms.

2, 1, 3, 71, 7, 10177, 2100001, 101770000001, 4603, 13, 107, 4013, 23, 3097349301044927552199565217412468305904367, 1847, 37, 367767021959, 54371, 3229, 17, 520063, 29, 389, 8059, 732713, 11, 7123120001, 137, 294563, 1656881076199062425029, 313583, 4817, 277

Offset: 1

Author

Amarnath Murthy, Jun 24 2004

Keywords

• base
• nonn

Comments

Conjecture:(1) Every concatenation is squarefree. (2) This is a rearrangement of the noncomposite numbers other than 5.

Conjecture (1) is false. 3^2 divides the concatenation for a(22) and a(30). - Sean A. Irvine, Nov 25 2009

Examples

			a(4) = 71 as 213 = 3*71.
		

Crossrefs

Cf. A096098.

Extensions

More terms from Sean A. Irvine, Nov 25 2009

a(30)-a(33) from Chai Wah Wu, Nov 29 2019