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A111348 Numbers n such that the result of swapping the 3rd and next to the next to the last digit of a number is prime. 2

%I #8 Nov 18 2014 12:54:12

%S 101,104,106,107,110,112,113,118,119,124,125,128,130,131,133,134,136,

%T 140,142,145,146,149,151,152,157,160,164,166,167,170,172,175,179,181,

%U 182,188,191,194,196,199,200,300,301,305,310,311,313,316,320,322,325

%N Numbers n such that the result of swapping the 3rd and next to the next to the last digit of a number is prime.

%C Similar to A095179 for the first few terms.

%C Since these numbers are just digit permutations of the primes the sequence is obviously infinite. - _Charles R Greathouse IV_, Oct 20 2008

%F For N1=a(n)*10^n+a(n-1)*10^(n-1)+a(n-2)*10^(n-2)+...+a(2)*10^2+a(1)*10 + a(0), N2=a(n)*10^n+a(n-1)*10^(n-1)+a(2)*10^(n-2)+...+a(n-2)*10^2+a(1)*10 + a(0) is prime.

%o (PARI) swapn(n,d) = \ d is the digit position to swap { local(j,ln,x,s,y,y2,tmp); for(x=10^(d-1),10^(d-1)+n, s = Str(x); ln = length(s); y = eval(Vec(s)); tmp=y[d]; y[d]=y[ln-d+1]; y[ln-d+1]=tmp; y2=0; for(j=1,ln, y2+=y[j]*10^(ln-j); ); if(isprime(y2),print1(x",")) ) }

%Y Cf. A095179, A111347, A111349.

%K easy,nonn,base

%O 1,1

%A _Cino Hilliard_, Nov 05 2005

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)