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A092993 Smallest prime of the form concatenation(s) of prime(n) with itself followed by a 3, or 0 if no such prime exists. 4
23, 0, 53, 73, 113, 13131313133, 173, 193, 233, 293, 313, 373, 41413, 433, 47474747474747474747474747473, 53535353535353535353535353533, 593, 613, 673, 71713, 733, 0, 83833, 89898989893, 97973, 1013, 1033, 1071071071073, 1093 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Start with p=prime(n). If concat(p,3) is prime, then this is a(n), else consider concat(p,p,3), and so on.

LINKS

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

EXAMPLE

For a(1), start with prime(1)=2. Since appending a digit 3 yields the prime 23, a(1)=23.

For a(2), start with prime(2)=3. Since concatenating any number of digits '3' never yields a prime, a(2)=0.

For a(6), starting with prime(6)=13, one has to take 5 concatenations of itself before a prime is obtained when a final digit '3' is appended, thus a(6)=13131313133.

a(22)=0 since the concatenation of prime(22)=79 with itself, followed by a 3, is always composite. - Giovanni Resta, Apr 07 2006

CROSSREFS

Cf. A092992, A092994, A092995.

Sequence in context: A180729 A119566 A143196 * A238331 A114784 A141517

Adjacent sequences: A092990 A092991 A092992 * A092994 A092995 A092996

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Mar 28 2004

EXTENSIONS

a(15)-a(21) from Stefan Steinerberger, Nov 09 2005

More terms from Giovanni Resta, Apr 07 2006

STATUS

approved

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Last modified January 29 18:23 EST 2023. Contains 359926 sequences. (Running on oeis4.)