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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A284045 Numbers k such that p = 6k-1 and q = 6k+1 are twin primes and (p^2 + q^2)/2 is prime. 1
 1, 25, 30, 40, 45, 70, 95, 215, 220, 385, 425, 455, 560, 565, 710, 775, 975, 980, 1060, 1130, 1500, 1540, 1605, 1755, 1815, 1995, 2280, 2305, 2335, 2425, 2705, 2775, 3010, 3020, 3090, 3190, 3230, 3600, 3640, 3895, 3945, 4455, 4480, 4615, 4900, 5045, 5495, 5525, 5750, 5880 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers k such that (6k)^2 + 1 is prime and p = 6k-1 and q = 6k+1 are twin primes. Numbers k such that p*q + 2 is prime, where p = 6k-1 and q = 6k+1 are twin primes. LINKS Robert G. Wilson v, Table of n, a(n) for n = 1..1000 FORMULA a(n) == 0 (mod 5) for n > 1. a(n+1) = 5 * A125251(n). MATHEMATICA fQ[n_] := AllTrue[{30n -1, 30n +1, 900n^2 +1}, PrimeQ]; Join[{1}, 5*Select[ Range@1200, fQ]] (* Robert G. Wilson v, Mar 19 2017 *) PROG (PARI) print1(1, ", "); for(n=1, 15000, if(isprime(30*n-1)&& isprime(30*n+1)&& isprime(900*n^2+1), print1(5*n, ", "))); CROSSREFS Subsequence of A002822. Cf. A051779. Sequence in context: A219258 A044861 A161835 * A213929 A167324 A307283 Adjacent sequences: A284042 A284043 A284044 * A284046 A284047 A284048 KEYWORD nonn AUTHOR Thomas Ordowski and Altug Alkan, Mar 19 2017 STATUS approved

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.

Last modified March 26 11:37 EDT 2023. Contains 361549 sequences. (Running on oeis4.)