A235689 Semiprimes which remain semiprimes when the leftmost and rightmost digits are removed.
141, 142, 143, 145, 146, 161, 166, 169, 194, 247, 249, 262, 265, 267, 291, 295, 298, 299, 341, 346, 361, 362, 365, 391, 393, 394, 395, 398, 445, 446, 447, 466, 469, 493, 497, 542, 543, 545, 562, 565, 566, 591, 597, 649, 662, 667, 669, 694, 695, 697, 698, 699
Offset: 1
Examples
169 = 13^2 is in the sequence because 6 = 2*3.
Programs
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Mathematica
Select[Range[100,700],PrimeOmega[#]==PrimeOmega[FromDigits[ Rest[ Most[ IntegerDigits[ #]]]]] ==2&] (* Harvey P. Dale, Nov 22 2018 *)
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PARI
list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358 delleft(a) = my(b, c); b=#Str(a); c=a\(10^(b-1)); a-c*(10^(b-1)) issemiprime(n) = n>0 && bigomega(n)==2 t=list(700); for(n=1, #t, if(issemiprime(delleft(t[n]\10)), print1(t[n],", ")))