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A247484 a(1)=8; for n>=1, a(n+1) is the smallest palindromic 3-almost prime with a(n) as a central substring.

%I A247484 #15 Dec 02 2014 20:56:36
%S A247484 8,282,52825,4528254,145282541,2214528254122,122145282541221,
%T A247484 51221452825412215,7512214528254122157,15751221452825412215751,
%U A247484 7157512214528254122157517,371575122145282541221575173,93715751221452825412215751739,3937157512214528254122157517393
%N A247484 a(1)=8; for n>=1, a(n+1) is the smallest palindromic 3-almost prime with a(n) as a central substring.
%C A247484 The 3-almost primes are the numbers that are the product of exactly three (not necessarily distinct) primes.
%e A247484 a(1) = 8 = 2*2*2;
%e A247484 a(2) = 282 = 2*3*47;
%e A247484 a(3) = 52825 = 5*5*2113;
%e A247484 a(4) = 4528254 = 2*3*754709.
%t A247484 d[n_]:=IntegerDigits[n];t = {x = 8}; Do[i = 1; While[!PrimeOmega[y = FromDigits[Flatten[{z = d[i], d[x], Reverse[z]}]]]==3, i++]; AppendTo[t, x = y], {n, 13}]; t
%Y A247484 Cf. A014612, A247483.
%K A247484 nonn,base
%O A247484 1,1
%A A247484 _Michel Lagneau_, Dec 01 2014