cp's OEIS Frontend

A064215 Least k such that k*6^n +/- 1 are twin primes.

%I A064215 #16 Sep 17 2015 06:21:13
%S A064215 1,2,2,2,18,3,33,255,212,115,147,102,17,33,308,87,198,33,172,418,210,
%T A064215 35,158,847,1010,292,157,1318,263,212,642,107,458,102,17,635,735,262,
%U A064215 2422,3517,1222,605,1362,227,367,602,207,2023,3925,1857,822,137,5568,928
%N A064215 Least k such that k*6^n +/- 1 are twin primes.
%C A064215 As n increases, a(n) is in average = 0.44*n^2. It appears that 62% of a(n)/n^2 are < 0.44. - _Pierre CAMI_, Jun 01 2012
%H A064215 R. J. Mathar, <a href="/A064215/b064215.txt">Table of n, a(n) for n = 1..240</a>
%p A064215 A064215 := proc(n)
%p A064215     for k from 1 do
%p A064215         if isprime(k*6^n-1) and isprime(k*6^n+1) then
%p A064215             return k;
%p A064215         end if;
%p A064215     end do:
%p A064215 end proc: # _R. J. Mathar_, Sep 17 2015
%t A064215 Table[ k = 1; While[ ! PrimeQ[ k*6^n + 1 ] || ! PrimeQ[ k*6^n - 1 ], k++ ]; k, {n, 50} ]
%Y A064215 Cf. A063983.
%K A064215 nonn
%O A064215 1,2
%A A064215 _Robert G. Wilson v_, Sep 21 2001