A171038 - OEIS

%I #12 Mar 31 2017 11:09:12

%S 2,3,5,4,11,13,14,19,23,29,31,34,71,73,74,53,59,61,64,41,43,49,83,89,

%T 94,101,103,104,109,113,124,131,134,139,179,151,154,163,164,143,149,

%U 181,191,193,194,199,211,223,224,229,233,239,271,251,254,263

%N In the sequence of prime numbers, replace all the '7' digits with '4' and vice versa.

%H Vincenzo Librandi, <a href="/A171038/b171038.txt">Table of n, a(n) for n = 1..1000</a>

%t fixp[n_]:=FromDigits[IntegerDigits[n]/.{7->a,4->b}/.{a->4,b->7}]; fixp/@Prime[Range[100]] (* _Harvey P. Dale_, Apr 25 2011 *)

%o (PARI) a(n)=my(v=[0,1,2,3,7,5,6,4,8,9]);subst(Pol(apply(k->v[k+1], digits(prime(n)))),'x,10) \\ _Charles R Greathouse IV_, Jul 25 2013

%K nonn,base,easy

%O 1,1

%A _N. J. A. Sloane_ and _Vincenzo Librandi_, Sep 04 2010