login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A193144 Primes of the form n^2 + n + 1, where n is semiprime. 1

%I #18 Jan 06 2013 19:06:07

%S 43,211,241,463,1123,1483,3307,3907,4831,6007,12433,14281,20023,20593,

%T 24181,26083,37831,41413,42643,43891,46441,47743,77563,82657,95791,

%U 98911,108571,145543,156421,158803,200257,205663,239611,284623,288907,304153,307471

%N Primes of the form n^2 + n + 1, where n is semiprime.

%C This is to semiprimes A001358 as A185632 is to nonprimes A018252.

%F {k: k is in A001358 and n^2 + n + 1 is in A000040}.

%e 43 is in the sequence because it is prime, and 43 = 6^2 + 6 + 1 where 6 = 2*3 is semiprime.

%t Select[#^2+#+1&/@Select[Range[1000],PrimeOmega[#]==2&],PrimeQ] (* _Harvey P. Dale_, Jan 06 2013 *)

%Y Cf. A000040, A001358, A185632, A192321.

%K nonn,easy

%O 1,1

%A _Jonathan Vos Post_, Dec 19 2012

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 25 01:35 EDT 2024. Contains 371964 sequences. (Running on oeis4.)