%I #8 Oct 04 2024 00:23:42
%S 4,9,25,49,121,403,1207,2701,7663,10201,17161,22801,32761,35143,36481,
%T 75007,97969,117907,124609,127087,139129,140209,146689,173809,197209,
%U 247021,257821,342127,382387,528529,573049,619369,635209,643063,692443,743623,844561,863041
%N Semiprimes whose prime factors are the digit reversal of each other.
%C The squares of all palindromic primes (A002385) are a subsequence and these are the only perfect squares.
%H Andrew Howroyd, <a href="/A376746/b376746.txt">Table of n, a(n) for n = 1..10000</a>
%e 121 is a term because 121 = 11 * 11.
%e 403 is a term because 403 = 13 * 31.
%e 1207 is a term because 1207 = 17 * 71.
%e 2701 is a term because 2701 = 37 * 73.
%o (PARI) upto(lim)={my(L=List()); forprime(p=2, sqrtint(lim), my(q=fromdigits(Vecrev(digits(p)))); if(isprime(q) && p*q<=lim, listput(L,p*q))); Set(L)}
%Y A083815 is a subsequence.
%Y Cf. A002385, A004086.
%K nonn,base
%O 1,1
%A _Andrew Howroyd_, Oct 03 2024