A279213 Primes formed by concatenating n with n-3.

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

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