A244607 - OEIS

%I #17 Oct 06 2019 17:21:03

%S 3,4,6,8,13,14,16,18,22,23,24,26,27,29,31,32,34,36,38,41,42,43,45,46,

%T 48,54,56,61,62,63,64,65,67,68,69,72,76,81,83,84,86,89,92,96,98,113,

%U 114,116,118,122,123,124,126,127,129,131,132,134,136,138,141,142,143,145,146

%N Numbers k such that (product of digits of k) - 1 is prime.

%C This sequence is infinite. With any number a(n), you can add infinitely many 1's to its decimal representation. E.g., 32 is in this sequence, so 321, 312, 3211, 32111, 31121, 11321, etc. are also terms of this sequence.

%C A number k is a term of this sequence iff A007954(k) is in A008864.

%H Jens Kruse Andersen, <a href="/A244607/b244607.txt">Table of n, a(n) for n = 1..10000</a>

%e 3*2 - 1 = 5 is prime. Thus 32 is a term of this sequence.

%o (PARI) for(n=1,10^3,d=digits(n);p=prod(i=1,#d,d[i]);if(isprime(p-1),print1(n,", ")))

%Y Cf. A007954, A008864, A089377, A081988.

%K nonn,base,easy

%O 1,1

%A _Derek Orr_, Jul 01 2014

%E Wrong term removed by _Jens Kruse Andersen_, Jul 13 2014