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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. 4
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 (list; graph; refs; listen; history; text; internal format)
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). [From Sean A. Irvine, Nov 25 2009]

LINKS

Table of n, a(n) for n=1..29.

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,more,nonn

AUTHOR

Amarnath Murthy, Jun 24 2004

EXTENSIONS

More terms from Sean A. Irvine, Nov 25 2009

STATUS

approved

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Last modified October 16 08:15 EDT 2019. Contains 328051 sequences. (Running on oeis4.)