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 A020755 #17 Mar 17 2025 07:02:41 %S A020755 2,5,10,51,246,849,22026,217077,1092755,8870033,221167433,47255689927, %T A020755 82462576233,1043460553378,79180770078563,3215226335143234, %U A020755 23742453640900989,125781000834058586 %N A020755 Increasing gaps between squarefree numbers (upper end). %C A020755 Up to n=10, a(n) is the upper end of the first gap of length n. However, for n=11 through n=16, a(n) is the upper end of the first gap of length n+1. See A020753. - _M. F. Hasler_, Dec 28 2015 %F A020755 a(n) = A020754(n) + A020753(n). - _M. F. Hasler_, Dec 28 2015 %e A020755 The first gap in A005117 occurs between 1 and 2 and has length 1. The next largest gap occurs between 3 and 5 and has length 2. The next largest gap is between 7 and 10 and has length 3. Etc. We are only interested in gaps that set new records. %o A020755 (PARI) A020755(n)=for(k=L=1,oo,issquarefree(k)||next;k-L>=n&&return(k);L=k) \\ _M. F. Hasler_, Dec 28 2015 %Y A020755 Cf. A005117, A020754, A020753, A045882, A051681. %K A020755 nonn,hard %O A020755 1,1 %A A020755 _David W. Wilson_ %E A020755 Thanks to Christian Bower for additional comments. %E A020755 More terms (computed using data from A020754) added by _M. F. Hasler_, Dec 28 2015