cp's OEIS Frontend

A132288 Odd palindromes which are semiprimes with an even number of digits.

%I A132288 #20 Jan 06 2025 04:13:47
%S A132288 33,55,77,1111,1441,1661,1991,3113,3223,3443,3883,7117,7447,7997,9119,
%T A132288 9229,9449,100001,103301,104401,107701,113311,115511,116611,124421,
%U A132288 125521,130031,136631,139931,146641,152251,157751,160061,163361,164461,169961,170071
%N A132288 Odd palindromes which are semiprimes with an even number of digits.
%C A132288 One of the divisors is 11 and the other is A132287(n).
%H A132288 Robert Israel, <a href="/A132288/b132288.txt">Table of n, a(n) for n = 1..10000</a>
%F A132288 a(n) = 11*A132287(n).
%p A132288 rev:= proc(n) local L,i; L:= convert(n,base,10); add(L[-i]*10^(i-1),i=1..nops(L)) end proc:
%p A132288 f:= proc(m) local A,i,j,k;
%p A132288   select(t -> isprime(t/11), [seq(seq(10^(m-1)*i + 10^(m/2)*j + rev(10^(m/2-1)*i+j),j=0 .. 10^(m/2-1)-1),i=[1,3,5,7, 9])])
%p A132288 end proc:
%p A132288 seq(op(f(m)),m=2..6,2); # _Robert Israel_, Jan 05 2025
%o A132288 (PARI) lista(nn) = {for(n=1, nn, if (ismo(n) && (bigomega(n) == 2), print1(n, ", ");););} \\ where ismo is isok in A132285 \\ _Michel Marcus_, Nov 05 2013
%Y A132288 Intersection of A132285 and A001358.
%Y A132288 Cf. A132286, A132287.
%K A132288 base,nonn
%O A132288 1,1
%A A132288 _Artur Jasinski_, Aug 16 2007
%E A132288 More terms from _Michel Marcus_, Nov 05 2013
%E A132288 Name edited by _Robert Israel_, Jan 05 2025