cp's OEIS Frontend

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.

A165986 Even semiprimes n such that (the largest prime factor of n) + 4 is prime.

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%I A165986 #22 Sep 08 2022 08:45:48
%S A165986 6,14,26,38,74,86,134,158,194,206,218,254,326,386,446,458,554,614,626,
%T A165986 698,758,794,878,914,926,974,998,1226,1286,1346,1478,1514,1538,1646,
%U A165986 1706,1718,1754,1766,1814,1874,1934,2018,2174,2186,2426,2558,2594,2606
%N A165986 Even semiprimes n such that (the largest prime factor of n) + 4 is prime.
%C A165986 Also numbers n of the form 2p such that p and p+4 are prime.
%C A165986 n is congruent to 2 modulo 3 for n > 6.
%H A165986 Harvey P. Dale, <a href="/A165986/b165986.txt">Table of n, a(n) for n = 1..1000</a>
%F A165986 a(n) = 2*A023200(n). - _R. J. Mathar_, Jun 23 2011
%t A165986 Select[Range[2,3000,2],PrimeOmega[#]==2&&PrimeQ[FactorInteger[#][[-1,1]]+4]&] (* _Harvey P. Dale_, Mar 09 2021 *)
%o A165986 (Magma) [ 2*p: p in PrimesUpTo(1500) | IsPrime(p+4) ]; // _Klaus Brockhaus_, Jun 26 2011
%o A165986 (PARI) forprime(p=2,1e3,if(isprime(p+4),print1(p+p", "))) \\ _Charles R Greathouse IV_, Jun 26 2011
%K A165986 nonn,easy
%O A165986 1,1
%A A165986 _Giovanni Teofilatto_, Oct 03 2009, Jun 26 2011
%E A165986 Definition clarified by _Harvey P. Dale_, Jul 14 2021