A088784 Primes formed by concatenating a prime with the preceding prime.

53, 5347, 5953, 6761, 137131, 179173, 211199, 223211, 239233, 263257, 359353, 541523, 593587, 613607, 631619, 653647, 659653, 757751, 809797, 977971, 997991, 1009997, 11091103, 11291123, 12371231, 13991381, 15591553, 17831777, 19311913, 19791973, 19931987, 23092297

Offset

1,1

Links

K. D. Bajpai, Table of n, a(n) for n = 1..10300

Example

a(2) = 5347 because 5347 is 53 (a prime) concatenated with 47 (the preceding prime).

Mathematica

concatpr[n_]:=FromDigits[Join[IntegerDigits[n], IntegerDigits[ NextPrime[ n, -1]]]]; Select[concatpr/@Prime[Range[400]], PrimeQ] (* Harvey P. Dale, May 12 2011 *)

Prog

(PARI) for(n=1, 10^3, p=prime(n); q=concat(Str(p), Str(precprime(p-1))); if(isprime(eval(q)), print1(q, ", "))) \\ Derek Orr, Aug 14 2014
(Python)
from itertools import islice
from sympy import isprime, nextprime
def agen(): # generator of terms
    p, pstr = 2, "2"
    while True:
        q = nextprime(p)
        qstr = str(q)
        t = int(qstr + pstr)
        if isprime(t):
            yield t
        p, pstr = q, qstr
print(list(islice(agen(), 32))) # Michael S. Branicky, Jan 05 2022

Crossrefs

Cf. A088712.

Sequence in context: A200917 A234630 A370294 * A104820 A093253 A293080

Adjacent sequences: A088781 A088782 A088783 * A088785 A088786 A088787

Keyword

base,nonn

Author

Chuck Seggelin (barkeep(AT)plasteredDragon.com), Oct 15 2003

Extensions

Terms a(30), a(31) and a(32) added by K. D. Bajpai, Aug 14 2014

Status

approved