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

1,1

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

Links

Table of n, a(n) for n=1..33.

Example

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

Crossrefs

Cf. A096098.

Sequence in context: A106485 A126008 A096098 * A212805 A246431 A225777

Adjacent sequences: A096094 A096095 A096096 * A096098 A096099 A096100

Keyword

base,nonn

Author

Amarnath Murthy, Jun 24 2004

Extensions

More terms from Sean A. Irvine, Nov 25 2009

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

Status

approved