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A279213 Primes formed by concatenating n with n-3. 1
41, 107, 1613, 2017, 3229, 4441, 4643, 5653, 7673, 9491, 106103, 116113, 124121, 130127, 136133, 170167, 172169, 182179, 184181, 196193, 206203, 212209, 214211, 220217, 224221, 230227, 272269, 274271, 280277, 302299, 304301, 320317, 322319, 326323, 334331 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Indranil Ghosh, Table of n, a(n) for n = 1..10000

EXAMPLE

For n = 16, n-3 = 13. Concatenating 16 and 13 gives 1613 which is a prime. So, 1613 is in the sequence. - Indranil Ghosh, Jan 23 2017

MATHEMATICA

Select[Table[FromDigits[Join[Flatten[IntegerDigits[{n, n -3}]]]], {n, 400}], PrimeQ]

PROG

(MAGMA) [m: n in [4..400 by 2] | IsPrime(m) where m is Seqint(Intseq(n-3) cat Intseq(n))];

(Python)

from sympy import isprime

i=4

j=1

while j<=10000:

....if isprime(int(str(i)+str(i-3)))==True:

........print str(j)+" "+str(i)+str(i-3)

........j+=1

....i+=1 # Indranil Ghosh, Jan 23 2017

(PARI) terms(n) = my(i=0, k=3); while(i < n, my(x=eval(Str(k, k-3))); if(ispseudoprime(x), print1(x, ", "); i++); k++)

/* Print initial 35 terms as follows: */

terms(35) \\ Felix Fröhlich, Jan 23 2017

CROSSREFS

Cf. A052089, A104332.

Sequence in context: A044609 A211494 A142054 * A070270 A001125 A116509

Adjacent sequences:  A279210 A279211 A279212 * A279214 A279215 A279216

KEYWORD

nonn,base

AUTHOR

Vincenzo Librandi, Dec 08 2016

STATUS

approved

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Last modified January 26 14:20 EST 2022. Contains 350598 sequences. (Running on oeis4.)