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A321422
Primes that are non-Chen primes whose reversal is a Chen prime.
0
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).
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
Sequence in context: A142675 A167187 A177095 * A133753 A177514 A137835
KEYWORD
nonn,base
AUTHOR
Paolo Galliani, Nov 09 2018
STATUS
approved