This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A290489 #22 Aug 06 2017 23:03:52 %S A290489 3,10,53,191,478,538,1082,1277,1346,2498,3299,5147,12889,20849,28277, %T A290489 31454,338098,520526,546461,1050706,1761289,1965077,3467038,6085103, %U A290489 27348949,27915898,111108917,113652593,230126531,231902434,327764249,438981203,581755523,1837981759,2489382911 %N A290489 Upper ends of record gaps between numbers that are either prime or twice a prime. %C A290489 The gap between 31397 and 31454 is due to the record prime gap between 31397 and 31469 being almost exactly twice the record prime gap between 15683 and 15727. %H A290489 Giovanni Resta, <a href="/A290489/b290489.txt">Table of n, a(n) for n = 1..40</a> %F A290489 a(n) = A290488(n) + A290541(n). %e A290489 a(3) = 53 because the next number that is a prime or twice a prime after 47 is 53, and that is a record gap of size 6. %t A290489 p = op = 2; r = 0; Reap[While[p < 10^6, p++; If[PrimeQ[p] || PrimeQ[p/2], g = p - op; If[g > r, Sow@p; r = g]; op = p]]][[2, 1]] (* _Giovanni Resta_, Aug 04 2017 *) %Y A290489 Cf. A001751, A290488, A290541. %K A290489 nonn %O A290489 1,1 %A A290489 _Bobby Jacobs_, Aug 03 2017 %E A290489 a(17)-a(35) from _Giovanni Resta_, Aug 04 2017