cp's OEIS Frontend

A339630 a(n) is the first number k such that there are exactly n ways to write 6*k = p + q with p a lesser twin prime (A001359) and q a greater twin prime (A006512), or 0 if there is no such k.

%I A339630 #15 Dec 13 2020 02:11:02
%S A339630 1,2,3,4,8,20,19,80,40,90,48,270,35,50,117,140,110,644,215,714,222,
%T A339630 430,345,350,315,850,390,930,620,1110,602,1040,385,2290,590,780,798,
%U A339630 910,735,990,1020,1700,700,770,595,1760,950,3380,875,5660,1330,1120,975,5970,1085,2990,1400,3980,1815,4570
%N A339630 a(n) is the first number k such that there are exactly n ways to write 6*k = p + q with p a lesser twin prime (A001359) and q a greater twin prime (A006512), or 0 if there is no such k.
%C A339630 If n is odd, a(n)/2 (if nonzero) is in A002822.
%H A339630 Robert Israel, <a href="/A339630/b339630.txt">Table of n, a(n) for n = 0..1330</a>
%F A339630 A339625(a(n)) = n if a(n) > 0.
%e A339630 a(4) = 8 because 6*8 = 48 can be written as p+q in exactly 4 ways: 48 = 5 + 43 = 17 + 31 = 29 + 19 = 41 + 7, and no smaller number has this property.
%p A339630 # given list A339625
%p A339630 T:= Array(0..max(A339625)):
%p A339630 for n from 1 to nops(A339625) do
%p A339630   if T[A339625[n]] = 0 then T[A339625[n]]:= n fi
%p A339630 od:
%p A339630 for k from 1 while T[k] <> 0 do od:
%p A339630 seq(T[i],i=0..k-1);
%Y A339630 Cf. A001359, A002822, A006512, A339625.
%K A339630 nonn
%O A339630 0,2
%A A339630 _J. M. Bergot_ and _Robert Israel_, Dec 10 2020