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 A308191 #47 Jun 24 2019 14:29:26 %S A308191 5,6,8,7,10,16,17,30,29,54,53,102,101,198,197,390,389,774,773,1542, %T A308191 3080,3079,6154,12304,24604,36901,73798,147592,295180,295517,591030, %U A308191 1182056,1574849,3149694,4728211,6299383,12598762,25197520,25197533,50395062,100790120,100790119,201580234,403160464,806320924,1232145821,2464291638 %N A308191 a(n) = smallest m such that A308190(m) = n, or -1 if no such m exists. %C A308191 It seems plausible that m exists for all n >= 0. %C A308191 From _Chai Wah Wu_, Jun 14 2019: (Start) %C A308191 All terms are even or prime. If a(n+1) is even, then 2*a(n)-a(n+1) = 4. a(n+1) <= 2*(a(n)-2) and thus m exists for all n >= 0. The proof in the comments of A308193 is applicable for this sequence as well. %C A308191 If a(n) is prime, then a(n-1) <= a(n) + 1. For the prime terms 7, 17, 29, 53, 101, 197, 389, 773, 3079, 100790119, a(n-1) = a(n) + 1. %C A308191 (End) %H A308191 Chai Wah Wu, <a href="/A308191/b308191.txt">Table of n, a(n) for n = 0..54</a> %Y A308191 Cf. A111234, A308190. %K A308191 nonn %O A308191 0,1 %A A308191 _N. J. A. Sloane_, Jun 14 2019 %E A308191 a(24)-a(41) from _Chai Wah Wu_, Jun 14 2019 %E A308191 a(42)-a(44) from _Chai Wah Wu_, Jun 15 2019 %E A308191 a(45)-a(46) from _Chai Wah Wu_, Jun 16 2019