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A051670 Smallest prime that concatenated with all previous terms of sequence forms a prime. 2
2, 3, 3, 3, 3, 23, 7, 3, 53, 19, 149, 571, 3, 131, 3, 151, 389, 31, 389, 97, 59, 277, 491, 181, 59, 67, 647, 1117, 797, 433, 41, 367, 29, 487, 719, 283, 347, 97, 1103, 193, 821, 13, 29, 31, 947, 619, 167, 229, 479, 271, 1217, 79, 2777, 241, 1361, 751, 83, 4603, 317 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

A. Murthy, Smar. Notions J. Vol. 11, N. 1-2-3 Spring 2000

LINKS

T. D. Noe, Table of n, a(n) for n=1..200

EXAMPLE

6th term of sequence is 23 because that is smallest prime that when concatenated with previous terms 2, 3, 3, 3, 3, produces a prime (2333323).

MATHEMATICA

nxt[{lst_, n_}]:=Module[{id=IntegerDigits[lst], np=2}, While[ !PrimeQ[ FromDigits[ Join[id, IntegerDigits[np]]]], np=NextPrime[np]]; {FromDigits[ Join[id, IntegerDigits[np]]], np}]; Transpose[NestList[nxt, {2, 2}, 60]] [[2]] (* Harvey P. Dale, May 25 2015 *)

CROSSREFS

Cf. A048549.

Sequence in context: A268607 A069603 A033679 * A089702 A089336 A089335

Adjacent sequences:  A051667 A051668 A051669 * A051671 A051672 A051673

KEYWORD

nonn,base,nice

AUTHOR

Felice Russo, Dec 15 1999

EXTENSIONS

Extended by T. D. Noe, May 01 2010

STATUS

approved

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Last modified February 25 22:55 EST 2020. Contains 332270 sequences. (Running on oeis4.)