cp's OEIS Frontend

A290572 Least number that is the start of a gap of size n between numbers that are either prime or twice a prime (A001751).

%I A290572 #24 Aug 26 2017 08:24:28
%S A290572 2,11,7,67,53,47,514,401,317,181,467,526,1069,2819,1262,3142,1382,
%T A290572 1913,1327,4178,2477,9697,8123,8329,3274,11213,21031,5119,16382,13063,
%U A290572 20446,44417,22193,37747,12854,46957,35617,63863,48679,20809,76166,39251,110359,59282,136898,212923,143006
%N A290572 Least number that is the start of a gap of size n between numbers that are either prime or twice a prime (A001751).
%C A290572 Numbers that are less than any later number are recorded in A290488.
%H A290572 Robert G. Wilson v, <a href="/A290572/b290572.txt">Table of n, a(n) for n = 1..261</a>
%H A290572 Robert G. Wilson v, <a href="/A290572/a290572.txt">Table of n, a(n) for n = 0..290, or 0 if no such value is known.</a>
%e A290572 a(1) is  2 since  3 -  2 = 1;
%e A290572 a(2) is 11 since 13 - 11 = 2;
%e A290572 a(3) is  7 since 10 -  7 = 3;
%e A290572 a(4) is 67 since 71 - 67 = 4; etc.
%t A290572 nxt[n_] := Block[{k = n +1}, While[ !PrimeQ[k] && !PrimeQ[k/2], k++]; k]; p = 2; q = 3; t[_] = 0; While[p < 215000, d = q - p; If[ t[d] == 0, t[d] = p]; p = q; q = nxt@ q]; t@# & /@ Range@ 47
%Y A290572 Cf. A001751, A002386, A290488, A290489.
%K A290572 nonn
%O A290572 1,1
%A A290572 _Bobby Jacobs_ and _Robert G. Wilson v_, Aug 06 2017