A247484
a(1)=8; for n>=1, a(n+1) is the smallest palindromic 3-almost prime with a(n) as a central substring.
Original entry on oeis.org
8, 282, 52825, 4528254, 145282541, 2214528254122, 122145282541221, 51221452825412215, 7512214528254122157, 15751221452825412215751, 7157512214528254122157517, 371575122145282541221575173, 93715751221452825412215751739, 3937157512214528254122157517393
Offset: 1
a(1) = 8 = 2*2*2;
a(2) = 282 = 2*3*47;
a(3) = 52825 = 5*5*2113;
a(4) = 4528254 = 2*3*754709.
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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
A248047
a(1)=88; for n>=1, a(n+1) is the smallest palindromic 4-almost prime with a(n) as a central substring.
Original entry on oeis.org
88, 1881, 218812, 12188121, 1121881211, 111218812111, 51112188121115, 1511121881211151, 815111218812111518, 78151112188121115187, 1781511121881211151871, 917815111218812111518719, 59178151112188121115187195, 9591781511121881211151871959
Offset: 1
a(1)=88=2*2*2*11;
a(2)=1881=3*3*11*19;
a(3)=218812=2*2*11*4973.
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d[n_]:=IntegerDigits[n]; t = {x = 88}; Do[i = 1; While[!PrimeOmega[y = FromDigits[Flatten[{z = d[i], d[x], Reverse[z]}]]]==4, i++]; AppendTo[t, x = y], {n, 14}]; t
A248165
a(1)=252; for n>=1, a(n+1) is the smallest palindromic 5-almost prime with a(n) as a central substring.
Original entry on oeis.org
252, 92529, 189252981, 1218925298121, 212189252981212, 12121892529812121, 8121218925298121218, 781212189252981212187, 1678121218925298121218761, 216781212189252981212187612, 22167812121892529812121876122, 2221678121218925298121218761222
Offset: 1
a(1) = 252 = 2*2*3*3*7;
a(2) = 92529 = 3*3*3*23*149.
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d[n_]:= IntegerDigits[n]; t = {x = 252}; Do[i = 1; While[!PrimeOmega[y = FromDigits[Flatten[{z = d[i], d[x], Reverse[z]}]]]==5, i++]; AppendTo[t, x = y], {n, 13}]; t
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