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.

101, 104, 106, 107, 110, 112, 113, 118, 119, 124, 125, 128, 130, 131, 133, 134, 136, 140, 142, 145, 146, 149, 151, 152, 157, 160, 164, 166, 167, 170, 172, 175, 179, 181, 182, 188, 191, 194, 196, 199, 200, 300, 301, 305, 310, 311, 313, 316, 320, 322, 325

Offset

1,1

Comments

Similar to A095179 for the first few terms.

Since these numbers are just digit permutations of the primes the sequence is obviously infinite. - Charles R Greathouse IV, Oct 20 2008

Links

Table of n, a(n) for n=1..51.

Formula

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.

Prog

(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", ")) ) }

Crossrefs

Cf. A095179, A111347, A111349.

Sequence in context: A330563 A060400 A128717 * A081649 A344802 A126118

Adjacent sequences: A111345 A111346 A111347 * A111349 A111350 A111351

Keyword

easy,nonn,base

Author

Cino Hilliard, Nov 05 2005

Status

approved