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 A306877 #16 Mar 21 2019 04:37:50 %S A306877 1870,935,1729,1045,374,2093,494,1235,2639,187,170,2737,190,247,4301, %T A306877 1265,110,2821,130,209,299,85,182,3367,418,95,3451,377,220,5423,230, %U A306877 1495,391,55,598,3458,238,65,133,253,260,403,266,115,5797,91,273,3689,741,319 %N A306877 Lexicographically earliest sequence of distinct positive terms such that, for any n > 0, among the prime divisors of n * a(n) there are at least 4 runs of consecutive prime numbers. %C A306877 This sequence is a variant of A285744 and of A306864. %C A306877 This sequence is a self-inverse permutation of the natural numbers. %H A306877 Rémy Sigrist, <a href="/A306877/b306877.txt">Table of n, a(n) for n = 1..30000</a> %H A306877 Rémy Sigrist, <a href="/A306877/a306877.gp.txt">PARI program for A306877</a> %H A306877 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %F A306877 A287170(n * a(n)) >= 4. %e A306877 The first terms, alongside the corresponding runs, are: %e A306877 n a(n) runs in n*a(n) %e A306877 -- ---- -------------- %e A306877 1 1870 2, 5, 11, 17 %e A306877 2 935 2, 5, 11, 17 %e A306877 3 1729 3, 7, 13, 19 %e A306877 4 1045 2, 5, 11, 19 %e A306877 5 374 2, 5, 11, 17 %e A306877 6 2093 2-3, 7, 13, 23 %e A306877 7 494 2, 7, 13, 19 %e A306877 8 1235 2, 5, 13, 19 %e A306877 9 2639 3, 7, 13, 29 %e A306877 10 187 2, 5, 11, 17 %e A306877 11 170 2, 5, 11, 17 %e A306877 12 2737 2-3, 7, 17, 23 %e A306877 13 190 2, 5, 13, 19 %e A306877 14 247 2, 7, 13, 19 %e A306877 15 4301 3-5, 11, 17, 23 %e A306877 16 1265 2, 5, 11, 23 %o A306877 (PARI) See Links section. %Y A306877 Cf. A285744, A287170, A306864. %K A306877 nonn,look %O A306877 1,1 %A A306877 _Rémy Sigrist_, Mar 14 2019