This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
2 is OK because 5^2 + 2^5 = 25 + 32 = 57 = 3*19 (semiprime).
IsSemiprime:=func< n|&+[k[2]: k in Factorization(n)] eq 2 >; [n: n in [1..85]|IsSemiprime(5^n+n^5)]; // Vincenzo Librandi, Dec 16 2010
Select[Range[100],PrimeOmega[5^# + #^5]==2&] (* Vincenzo Librandi, May 21 2014 *)
2 is in the sequence because 7^2 + 2^7 = 177 = 3*59 (semiprime). 12 is in the sequence because 7^12 + 12^7 = 13*1067470693 (semiprime). [_Vincenzo Librandi_, Dec 16 2010]
IsSemiprime:=func; [n: n in [1..85] | IsSemiprime(7^n+n^7)] // Vincenzo Librandi, Dec 16 2010
4 is OK because 3^4 + 4^3 = 81 + 64 = 145 = 5*29 (semiprime).
IsSemiprime:=func< n | &+[ k[2]: k in Factorization(n) ] eq 2 >; [ n: n in [1..95] | IsSemiprime(3^n+n^3)]; // Vincenzo Librandi Dec 16 2010
Select[Range[100], PrimeOmega[3^# + #^3]==2&] (* Vincenzo Librandi, May 21 2014 *)
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