A101783 Lower bound twin primes such that their digital reverse is prime and a lower bound twin prime.

3, 5, 11, 17, 71, 101, 191, 1031, 1301, 7349, 7457, 7547, 7589, 9437, 9857, 10007, 10067, 10301, 10457, 10859, 11057, 11717, 11777, 11939, 12107, 12821, 13931, 14081, 14549, 14591, 16061, 16361, 16829, 17417, 18041, 19541, 19697, 19991

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..2500

Example

17 is a lower bound twin prime and the reverse,71, is prime and also a lower bound twin prime.

Mathematica

lbtpQ[n_]:=Module[{rp=FromDigits[Reverse[IntegerDigits[n]]]}, PrimeQ[rp] &&PrimeQ[rp+2]]; Select[Transpose[Select[Partition[Prime[Range[2300]], 2, 1], Last[#]-First[#]==2&]][[1]], lbtpQ] (* Harvey P. Dale, Jan 27 2012 *)

Prog

(PARI) twlrpr2(n) = { for(x=1, n, y=twinl(x); z=eval(rev(y)); if(isprime(z) && isprime(z+2), print1(y", ")) ) } twinl(n) = \The n-th upper twin prime { local(c, x); c=0; x=1; while(c<n, if(isprime(prime(x)+2), c++); x++; ); return(prime(x)) }
rev(str) = \\ Get the reverse of the input string
{ local(tmp, s, j); tmp = Vec(Str(str)); s=""; forstep(j=length(tmp), 1, -1, s=concat(s, tmp[j])); return(s) }

Crossrefs

Sequence in context: A283399 A216181 A101781 * A078883 A355901 A155990

Adjacent sequences: A101780 A101781 A101782 * A101784 A101785 A101786

Keyword

easy,nonn,base

Author

Cino Hilliard, Jan 26 2005

Status

approved