A100759 Beginning with 2, least prime not occurring earlier such that the concatenation of first n terms has the least prime factor prime(n).

2, 7, 5, 17, 127, 3, 347, 37, 71, 829, 89, 79, 311, 271, 1103, 823, 827, 7219, 149, 499, 3947, 6367, 2861, 3673, 13781, 2281, 281, 229, 353, 1597, 191, 1879, 2609, 10993, 19961, 4789, 383, 1093, 521, 13681, 9227, 12619, 8219, 12037, 8573, 7621, 6029

Offset

1,1

Comments

Conjecture: Every prime is a member.

Links

Table of n, a(n) for n=1..47.

Example

a(1) = 2, a(2) = 7 and the least prime divisor of 27 is 3.

Mathematica

a = {2}; b = 2; Do[i = 1; While[Length[Intersection[a, {Prime[i]}]] == 1, i++ ]; While[ !FactorInteger[FromDigits[Join[IntegerDigits[b], IntegerDigits[Prime[i]]]]][[1, 1]] == Prime[n], i++ ]; AppendTo[a, Prime[i]]; b = FromDigits[Join[IntegerDigits[b], IntegerDigits[Prime[i]]]], {n, 2, 30}]; a (* Stefan Steinerberger, Dec 21 2007 *)

Crossrefs

Cf. A114025.

Sequence in context: A233248 A114025 A135566 * A205448 A180510 A152555

Adjacent sequences: A100756 A100757 A100758 * A100760 A100761 A100762

Keyword

base,less,nonn

Author

Amarnath Murthy, Nov 23 2004

Extensions

More terms from Stefan Steinerberger, Dec 21 2007

More terms from David Wasserman, Mar 04 2008

Status

approved