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 A276481 Numbers n such that b(n) is a prime, where b(1) = prime(1) = 2, b(n) = 10*b(n-1) + (prime(n) mod 10). 0
 1, 2, 4, 13, 16, 17, 28, 34, 90, 100, 132, 331, 534, 7923 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Primes in the sequence b(n) are 2, 23, 2357, 2357137939171, ... LINKS MAPLE Res:= NULL: p:= 0: b:= 0: for n from 1 to 600 do   p:= nextprime(p);   b:= 10*b + (p mod 10);   if isprime(b) then Res:= Res, n fi od: Res; # Robert Israel, Sep 05 2016 MATHEMATICA b[1] = Prime@ 1; b[n_] := b[n] = 10 b[n - 1] + Mod[Prime@ n, 10]; Select[Range[10^3], PrimeQ@ b[#] &] (* Michael De Vlieger, Sep 06 2016 *) PROG (PARI) b(n) = if (n==1, 2, 10*b(n-1) + (prime(n) % 10)); isok(n) = isprime(b(n)); \\ Michel Marcus, Sep 05 2016 (PARI) list(lim)=my(v=List(), s, n); forprime(p=2, , if(n++>lim, return(Vec(v))); if(ispseudoprime(s=10*s+p%10), listput(v, n))) \\ Charles R Greathouse IV, Sep 05 2016 CROSSREFS Cf. A007652, A069151. Sequence in context: A116662 A024580 A074097 * A287684 A033628 A077319 Adjacent sequences:  A276478 A276479 A276480 * A276482 A276483 A276484 KEYWORD nonn,base AUTHOR Thomas Ordowski, Sep 05 2016 EXTENSIONS a(7)-a(13) from Michel Marcus, Sep 05 2016 a(14) from Robert Israel, Sep 05 2016 STATUS approved

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Last modified September 19 02:20 EDT 2021. Contains 347550 sequences. (Running on oeis4.)