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).

1, 2, 4, 13, 16, 17, 28, 34, 90, 100, 132, 331, 534, 7923

Offset

1,2

Comments

Primes in the sequence b(n) are 2, 23, 2357, 2357137939171, ...

Links

Table of n, a(n) for n=1..14.

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