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 A339580 #34 Dec 25 2020 10:41:42 %S A339580 1,3,90,1122660,19099920,85864770,26089808580,554688278430, %T A339580 4090932431513070,95405042230542330 %N A339580 Indices of records in A339579. %C A339580 The records themselves begin 4,5,6,7,8,9,10,12,13,14. %C A339580 a(11) <= 90616211958465842220. %D A339580 Carl Pomerance, Problem 81:21 (= 321), in R. K. Guy problem list. %H A339580 R. K. Guy, editor, <a href="/A339579/a339579.pdf">Western Number Theory Problems, 1985-12-21 & 23</a>, Typescript, Jul 13 1986, Dept. of Math. and Stat., Univ. Calgary, 11 pages. Annotated scan of pages 1, 3, 7, 9, with permission. %F A339580 a(n) = A339581(n) + 1 for n >= 2. - _David A. Corneth_, Dec 24 2020 %e A339580 90 is in the sequence as A339579(90) = 6 (90*2^k - 1 is prime for k = 0..5 and composite for k = 6) and A339579(m) < 6 for m < 90. - _David A. Corneth_, Dec 24 2020 %Y A339580 Cf. A063377, A124514, A125113, A339579, A339581. %K A339580 nonn,more %O A339580 1,2 %A A339580 _N. J. A. Sloane_, Dec 24 2020 %E A339580 a(8)-a(10) were taken from A057331 and the bound on a(11) was taken from A005602. - _David A. Corneth_ and _Amiram Eldar_, Dec 25 2020