cp's OEIS Frontend

A117093 Numbers k such that nextprime(3*k) > 3*nextprime(k) (if p is prime then nextprime(p) = p).

%I A117093 #22 Jul 26 2025 10:02:32
%S A117093 2,3,5,7,11,13,16,17,18,19,23,28,29,30,31,37,38,39,40,41,43,47,53,58,
%T A117093 59,61,67,71,72,73,78,79,81,82,83,88,89,95,96,97,98,99,100,101,103,
%U A117093 106,107,108,109,113,127,130,131,137,138,139,148,149,150,151,156,157
%N A117093 Numbers k such that nextprime(3*k) > 3*nextprime(k) (if p is prime then nextprime(p) = p).
%C A117093 Includes all primes.
%H A117093 Robert Israel, <a href="/A117093/b117093.txt">Table of n, a(n) for n = 1..10000</a>
%e A117093 13 is a term since nextprime(3*13) = 41 and 3*nextprime(13) = 3*13=39 and 41 > 39.
%p A117093 filter:= n -> nextprime(3*n) > 3*nextprime(n-1):
%p A117093 select(filter, [$1..1000]); # _Robert Israel_, Jul 25 2025
%t A117093 fp[k_]:=If[PrimeQ[k],k,NextPrime[k]];Select[Range[160],fp[3#]>3fp[#]&] (* _James C. McMahon_, Aug 23 2024 *)
%o A117093 (PARI) for(i=1,100,if(nextprime(3*i)>nextprime(3)*nextprime(i),print1(i,", ")))
%Y A117093 Union of A000040 and A117100.
%Y A117093 Cf. A007918 (nextprime).
%K A117093 easy,nonn
%O A117093 1,1
%A A117093 Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 18 2006
%E A117093 a(44)-a(59) from _James C. McMahon_, Aug 23 2024