login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons 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
43, 211, 241, 463, 1123, 1483, 3307, 3907, 4831, 6007, 12433, 14281, 20023, 20593, 24181, 26083, 37831, 41413, 42643, 43891, 46441, 47743, 77563, 82657, 95791, 98911, 108571, 145543, 156421, 158803, 200257, 205663, 239611, 284623, 288907, 304153, 307471 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..37.

FORMULA

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

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A000040, A001358, A185632, A192321.

Sequence in context: A145650 A142527 A142161 * A142659 A140041 A264821

Adjacent sequences:  A193141 A193142 A193143 * A193145 A193146 A193147

KEYWORD

nonn,easy

AUTHOR

Jonathan Vos Post, Dec 19 2012

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 16 22:18 EDT 2021. Contains 343957 sequences. (Running on oeis4.)