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 A020755 Increasing gaps between squarefree numbers (upper end). 5

%I

%S 2,5,10,51,246,849,22026,217077,1092755,8870033,221167433,47255689927,

%T 82462576233,1043460553378,79180770078563,3215226335143234,

%U 23742453640900989,125781000834058586

%N Increasing gaps between squarefree numbers (upper end).

%C 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 a(n) = A020754(n) + A020753(n). - _M. F. Hasler_, Dec 28 2015

%e 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 (PARI) A020755(n)=for(k=L=1,9e9,issquarefree(k)||next;k-L>=n&&return(k);L=k) \\ _M. F. Hasler_, Dec 28 2015

%Y Cf. A005117, A020754, A020753, A045882, A051681.

%K nonn,hard

%O 1,1

%A _David W. Wilson_