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A307046 Numbers k such that k^2 reversed is a prime and k^2 + (k^2 reversed) is a semiprime.

%I A307046 #44 Apr 02 2019 11:57:20
%S A307046 4,28,40,62,106,140,193,196,274,316,334,400,410,554,556,620,862,866,
%T A307046 874,884,962,1004,1025,1066,1154,1174,1190,1205,1256,1274,1294,1360,
%U A307046 1390,1394,1396,1400,1744,1784,1816,1844,1891,1900,1927,1960,1981,1988,2672,2696,2710,2722,2740,2786,2800,3016,3026
%N A307046 Numbers k such that k^2 reversed is a prime and k^2 + (k^2 reversed) is a semiprime.
%H A307046 Robert Israel, <a href="/A307046/b307046.txt">Table of n, a(n) for n = 1..10000</a>
%e A307046 4^2=16, reversed is 61. 16+61=77 which is semiprime (7*11), so 4 is in this sequence.
%p A307046 revdigs:= proc(n) local L,i;
%p A307046 L:= convert(n,base,10);
%p A307046 add(L[-i]*10^(i-1),i=1..nops(L))
%p A307046 end proc:
%p A307046 filter:= proc(n) local a,b;
%p A307046 a:= n^2;
%p A307046 b:= revdigs(a);
%p A307046 isprime(b) and numtheory:-bigomega(a+b)=2
%p A307046 end proc:
%p A307046 select(filter, [$1..10000]); # _Robert Israel_, Mar 31 2019
%t A307046 Select[Range[50000],
%t A307046 PrimeQ[IntegerReverse[#^2]] &&
%t A307046    PrimeOmega[#^2 + IntegerReverse[#^2]] == 2 &]
%Y A307046 Cf. A007488, A059007, A306301.
%K A307046 nonn,base
%O A307046 1,1
%A A307046 _Robert Price_, Mar 31 2019