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 A319141 Prime numbers p such that p squared + p reversed is also prime. 1
 211, 223, 271, 283, 433, 463, 691, 823, 859, 2017, 2029, 2251, 2269, 2293, 2341, 2347, 2593, 2647, 2833, 2851, 2857, 2887, 4153, 4327, 4507, 4513, 4903, 6091, 6361, 6421, 6481, 6529, 6871, 6949, 8011, 8059, 8161, 8209, 8287, 8419, 8467, 8707, 8803, 8929, 8971 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms == 1 (mod 6). - Robert Israel, Sep 13 2018 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE 271 belongs to this sequence as 271 squared is 73441 and 271 reversed is 172 and the sum of 73441 and 172 is 73613, which is prime. MAPLE revdigs:= proc(n) local L, i;   L:= convert(n, base, 10);   add(L[-i]*10^(i-1), i=1..nops(L)); end proc: filter:= t -> isprime(t) and isprime(t^2+revdigs(t)): select(filter, [seq(t, t=1..10^4, 6)]); # Robert Israel, Sep 13 2018 MATHEMATICA Select[Prime@Range@1120, PrimeQ[#^2 + FromDigits[Reverse@IntegerDigits@#]] &] (* Vincenzo Librandi, Sep 14 2018 *) PROG (Python) nmax=10000 def is_prime(num):     if num == 0 or num == 1: return(0)     for k in range(2, num):        if (num % k) == 0:            return(0)     return(1) ris = "" for i in range(nmax):     if is_prime(i):        r=int((str(i)[::-1]))        t=pow(i, 2)+r        if is_prime(t):           ris = ris+str(i)+", " print(ris) (PARI) forprime(p=1, 9000, if(ispseudoprime(p^2 + eval(concat(Vecrev(Str(p))))), print1(p, ", "))) \\ Felix FrÃ¶hlich, Sep 12 2018 CROSSREFS Cf. A304390. Sequence in context: A108406 A051268 A159911 * A133959 A133960 A031931 Adjacent sequences:  A319138 A319139 A319140 * A319142 A319143 A319144 KEYWORD nonn,base,look AUTHOR Pierandrea Formusa, Sep 11 2018 STATUS approved

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Last modified January 17 17:47 EST 2022. Contains 350402 sequences. (Running on oeis4.)