A227948 - OEIS

%I #19 Apr 06 2015 03:14:52

%S 21,23,27,29,81,83,253,293,299,343,347,349,431,437,439,471,473,477,

%T 529,623,653,659,677,743,893,1123,1219,1253,1257,1297,1423,1489,1521,

%U 1523,1529,1587,1589,1657,1763,1853,1867,1927,2151,2167,2239,2277,2279,2321,2327,2329,2377,2413,2443,2459,2467,2497,2543,2569

%N Zeroless numbers n such that n + (product of digits of n) and n - (product of digits of n) are prime.

%C Intersection of A157676 and A229221 (without the primes containing zero digits).

%e 29 - 2*9 = 11 (prime) and 29 + 2*9 = 47 (prime) so 29 is a member of this sequence.

%e 743 - 7*4*3 = 659 (prime) and 743 + 7*4*3 = 827 (prime) so 743 is a member of this sequence.

%o (Python)

%o from sympy import isprime

%o def DP(n):

%o ..p = 1

%o ..for i in str(n):

%o ....p *= int(i)

%o ..return p

%o {print(n,end=', ') for n in range(5000) if DP(n) and isprime(n+DP(n)) and isprime(n-DP(n))}

%o ## Simplified by _Derek Orr_, Apr 05 2015

%o (PARI) for(n=1,5000,d=digits(n);p=prod(i=1,#d,d[i]);if(p&&isprime(n+p)&&isprime(n-p),print1(n,", "))) \\ _Derek Orr_, Apr 05 2015

%Y Cf. A157676, A229221, A007954, A052382.

%K nonn,base,easy

%O 1,1

%A _Derek Orr_, Oct 04 2013

%E More terms from _Derek Orr_, Apr 05 2015