login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A245590 Primes p such that p^2 + 6 is a semiprime. 1
2, 3, 7, 17, 23, 41, 47, 53, 59, 101, 149, 157, 173, 179, 193, 211, 229, 233, 239, 241, 251, 311, 347, 349, 353, 359, 373, 379, 383, 389, 409, 421, 439, 443, 457, 479, 499, 509, 521, 541, 571, 577, 599, 619, 641, 661, 691, 701, 719, 751, 761, 769, 809, 823, 829 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..11200

EXAMPLE

7 is in the sequence because it is prime and 7^2 + 6 = 55 = 5 * 11, which is semiprime.

23 is in the sequence because it is prime and 23^2 + 6 = 535 = 5 * 107, which is semiprime.

MAPLE

with(numtheory):A245590:=n->`if`(isprime(n) and bigomega(n^2+6)=2, n, NULL): seq(A245590 (n), n=1..1500);

MATHEMATICA

Select[Prime[Range[200]], PrimeOmega[#^2 + 6] == 2 &]

PROG

(PARI)

forprime(p=1, 10^4, if(bigomega(p^2+6)==2, print1(p, ", "))) \\ Derek Orr, Aug 03 2014

CROSSREFS

Cf. A000040, A001358.

Cf. A109953 (primes p: p^2 + 2 is semiprime).

Cf. A243365 (primes p: p^2 + 6 and p^2 - 6  are semiprimes).

Sequence in context: A019335 A113425 A289379 * A110480 A268539 A083822

Adjacent sequences:  A245587 A245588 A245589 * A245591 A245592 A245593

KEYWORD

nonn,easy

AUTHOR

K. D. Bajpai, Jul 26 2014

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 October 20 20:08 EDT 2019. Contains 328271 sequences. (Running on oeis4.)