cp's OEIS Frontend

A356221 Position of second appearance of 2n in the sequence of prime gaps A001223; if 2n does not appear at least twice, a(n) = -1.

%I A356221 #8 Aug 08 2022 15:54:44
%S A356221 3,6,11,72,42,47,62,295,180,259,297,327,446,462,650,1315,1059,1532,
%T A356221 4052,2344,3732,3861,8805,7234,4754,2810,4231,14124,5949,9834,17200,
%U A356221 10229,19724,25248,15927,30765,42673,28593,24554,50523,44227,44390,29040,89715,47350
%N A356221 Position of second appearance of 2n in the sequence of prime gaps A001223; if 2n does not appear at least twice, a(n) = -1.
%C A356221 Prime gaps (A001223) are the differences between consecutive prime numbers. They begin: 1, 2, 2, 4, 2, 4, 2, 4, 6, ...
%t A356221 nn=1000;
%t A356221 gaps=Differences[Array[Prime,nn]];
%t A356221 mnrm[s_]:=If[Min@@s==1,mnrm[DeleteCases[s-1,0]]+1,0];
%t A356221 Table[Position[gaps,2*n][[2,1]],{n,mnrm[Select[Range[nn],Length[Position[gaps,2*#]]>=2&]]}]
%Y A356221 The position of the first (instead of second) appearance of 2n is A038664.
%Y A356221 Column k = 2 of A356222.
%Y A356221 The position of the n-th appearance of 2n is A356223.
%Y A356221 A001223 lists the prime gaps, reduced A028334.
%Y A356221 A073491 lists numbers with gapless prime indices.
%Y A356221 A274121 counts appearances of the n-th prime gap in those prior.
%Y A356221 A356226 gives the lengths of maximal gapless intervals of prime indices.
%Y A356221 Cf. A029709, A066205, A137921, A193829, A287170, A328335, A328457, A356224, A356225.
%K A356221 nonn
%O A356221 1,1
%A A356221 _Gus Wiseman_, Aug 02 2022