This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A199980 #18 Nov 05 2020 19:22:11
%S A199980 2,37,43,73,137,173,211,223,317,367,389,431,673,827,839,929,983,1223,
%T A199980 1279,1297,1367,1447,1621,1637,1693,1999,2111,2161,2179,2213,2269,
%U A199980 2339,2393,2663,2699,2719,2791,2917,2969,2971,3167,3169,3221,3329,3463,3499,3617
%N A199980 Primes whose multiplicative digital root is 2.
%C A199980 Complement of A199981 with respect to A034049, numbers whose multiplicative digital root is 2.
%H A199980 Robert Israel, <a href="/A199980/b199980.txt">Table of n, a(n) for n = 1..10000</a>
%e A199980 Prime 389 is in sequence because 3*8*9=216, 2*1*6 =12, 1*2=2.
%p A199980 mdr:= proc(n) option remember;
%p A199980 local t;
%p A199980 t:= convert(convert(n,base,10),`*`);
%p A199980 if t < 10 then t else procname(t) fi
%p A199980 end proc:
%p A199980 select(t -> mdr(t) = 2 and isprime(t), [2, seq(i,i=3..10000,2)]); # _Robert Israel_, Nov 05 2020
%t A199980 t = {}; n = 0; While[Length[t] < 100, n = NextPrime[n]; s = n; While[s >= 10, s = Times @@ IntegerDigits[s]]; If[s == 2, AppendTo[t, n]]]; t (* _T. D. Noe_, Nov 15 2011 *)
%t A199980 Select[Prime[Range[600]],FixedPoint[Times@@IntegerDigits[#]&,#]==2&] (* _Harvey P. Dale_, Mar 28 2012 *)
%Y A199980 Cf. A199981 (nonprime numbers whose multiplicative digital root is 2).
%Y A199980 Includes A107612.
%Y A199980 Cf. A031347, A034049.
%K A199980 nonn,base
%O A199980 1,1
%A A199980 _Jaroslav Krizek_, Nov 13 2011