A252788
Numbers m such that 3^m + m is a semiprime.
Original entry on oeis.org
1, 4, 7, 14, 16, 20, 22, 32, 38, 55, 80, 92, 188, 220, 296, 328, 370, 422, 452, 454, 500, 650, 934, 962
Offset: 1
1 is in this sequence because 3^1+1 = 2*2 is semiprime.
14 is in this sequence because 3^14+14 = 283*16901 and these two factors are prime.
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IsSemiprime:=func; [m: m in [1..130] | IsSemiprime(s) where s is 3^m+m];
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Select[Range[130], PrimeOmega[3^# + #]==2 &]
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first(m)=my(v=vector(m),r=1);for(i=1,m,while(bigomega(3^r + r)!=2,r++);v[i]=r;r++);v; \\ Anders Hellström, Aug 14 2015
A089535
Semiprimes of the form 2^k + k.
Original entry on oeis.org
6, 2059, 8388631, 17179869218, 576460752303423547, 590295810358705651781, 154742504910672534362390615, 39614081257132168796771975263, 664613997892457936451903530140172407, 10633823966279326983230456482242756731, 680564733841876926926749214863536423041
Offset: 1
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Select[Table[2^k+k,{k,200}],PrimeOmega[#]==2&] (* Harvey P. Dale, Aug 11 2024 *)
A089536
Lesser prime factor of semiprimes in A089535.
Original entry on oeis.org
2, 29, 31, 2, 7, 7, 5, 1188359, 1307, 165864626101044727, 36120307175753, 9772772454840984668059, 8944440848667088469951, 3041407, 6446147951, 48370466980471484946806147635774599979591, 24025609733, 11, 15866068029777944368693, 50031370538856249715800928172618839
Offset: 1
Offset changed to 1 and more terms from
Jinyuan Wang, Jul 30 2021
A089537
Greater prime factor of semiprimes in A089535.
Original entry on oeis.org
3, 71, 270601, 8589934609, 82351536043346221, 84327972908386521683, 30948500982134506872478123, 33335112753917098113257, 508503441386731397438334759097301, 64111463765644650653, 18841609804988852361375097, 306274945731599108294378939441, 22457217721139859611914512110646173819
Offset: 1
Offset changed to 1 and more terms from
Jinyuan Wang, Jul 30 2021
Showing 1-4 of 4 results.
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