A321422 Primes that are non-Chen primes whose reversal is a Chen prime.

73, 733, 739, 967, 1021, 1103, 1153, 1223, 1237, 1453, 1523, 1657, 1723, 1741, 1831, 3023, 3911, 7057, 7187, 7523, 7577, 7643, 7673, 7699, 7717, 7841, 9161, 9173, 9293, 9497, 9679, 9749, 9803, 9833, 9883, 9923, 9931, 10151, 10273, 10453, 10853, 11003, 11083, 11243, 11423

Offset

1,1

Comments

The second term of the sequence: 733 is congruent to 1 mod 61, to 2 mod 43, to 3 mod 73, where 61 is the second non-Chen prime, 43 is the first non-Chen prime and 73 is the third non-Chen prime. 733 is also congruent to 4 mod (3^6).

Links

Table of n, a(n) for n=1..45.

Mathematica

cpQ[n_] := Module[{rev = FromDigits[Reverse[IntegerDigits[n]]]}, PrimeOmega[n + 2] > 2 && PrimeQ[rev] && PrimeOmega[rev + 2] < 3]; Select[Prime[Range[1300]], cpQ] (* Amiram Eldar, Nov 09 2018 after Harvey P. Dale at A118725 *)

Prog

(PARI) forprime(p=1, 10^4, w=Vecrev(digits(p)); q=0; for(j=1, length(w), q=q*10+w[j]); if(ispseudoprime(q)==1, if(bigomega(p+2)>2, if(bigomega(q+2)<=2, print1(p, ", ")))))

Crossrefs

Cf. A109611, A102540.

Sequence in context: A142675 A167187 A177095 * A133753 A177514 A137835

Adjacent sequences: A321419 A321420 A321421 * A321423 A321424 A321425

Keyword

nonn,base

Author

Paolo Galliani, Nov 09 2018

Status

approved