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A337047 Numbers k such that A001414(k) and A001414(A004086(k)) are twin primes p, p+2.

%I A337047 #15 Feb 06 2021 21:59:27
%S A337047 405,412,850,25315,49419,50127,224315,293394,308700,697136,801350,
%T A337047 811910,997425,1118520,1152000,1177250,1550520,1659350,1725332,
%U A337047 1739640,1824500,1976895,2141150,2580640,2580831,3530466,3718376,4050405,4459455,4536532,4577732,4832796,5173100,5510287,5601570,5603989,5609439
%N A337047 Numbers k such that A001414(k) and A001414(A004086(k)) are twin primes p, p+2.
%H A337047 Robert Israel, <a href="/A337047/b337047.txt">Table of n, a(n) for n = 1..150</a>
%e A337047 a(3)=850 is in the sequence because A001414(850)=2+5+5+17=29, A001414(58)=2+29=31, and (29,31) is a pair of twin primes.
%p A337047 revdigs:= proc(n) local L,k;
%p A337047   L:= convert(n,base,10);
%p A337047   add(L[-k]*10^(k-1),k=1..nops(L))
%p A337047 end proc:
%p A337047 filter:= proc(n) local a,b;
%p A337047   a:= convert(map(convert,ifactors(n)[2],`*`),`+`);
%p A337047   if not isprime(a) then return false fi;
%p A337047   b:= convert(map(convert,ifactors(revdigs(n))[2],`*`),`+`);
%p A337047   b = a+2 and isprime(b)
%p A337047 end proc:
%p A337047 select(filter, [$1 .. 10^7]);
%Y A337047 Cf. A001097, A001414, A004086. Subsequence of A100118.
%K A337047 nonn,base
%O A337047 1,1
%A A337047 _J. M. Bergot_ and _Robert Israel_, Aug 12 2020