cp's OEIS Frontend

A100384 a(n) = the smallest number x >= 2 such that for m = x to x + n - 1, A006530(m) increases.

%I A100384 #24 Dec 05 2022 20:45:43
%S A100384 2,2,8,8,90,168,9352,46189,721970,721970,6449639,565062156,
%T A100384 11336460025,37151747513,256994754033
%N A100384 a(n) = the smallest number x >= 2 such that for m = x to x + n - 1, A006530(m) increases.
%C A100384 A006530(m) is the largest prime factor of m.
%C A100384 a(16) > 3*10^11. - _Donovan Johnson_, Oct 24 2009
%C A100384 a(16) > 10^13. - _Giovanni Resta_, Jul 25 2013
%e A100384 a(5)=90 because the largest prime factors of 90,91,92,93,94 are 5,13,23,31,47.
%o A100384 (Python)
%o A100384 from sympy import factorint
%o A100384 def A100384(n):
%o A100384     k, a = 2, [max(factorint(m+2)) for m in range(n)]
%o A100384     while True:
%o A100384         for i in range(1, n):
%o A100384             if a[i-1] >= a[i]:
%o A100384                 break
%o A100384         else:
%o A100384             return k
%o A100384         a = a[i:] + [max(factorint(k+j+n)) for j in range(i)]
%o A100384         k += i # _Chai Wah Wu_, Jul 24 2017
%Y A100384 Cf. A006530, A070089, A071869, A100376, A100385, A358890.
%K A100384 nonn,more
%O A100384 1,1
%A A100384 _Labos Elemer_, Dec 09 2004
%E A100384 Edited by _Don Reble_, Jun 13 2007
%E A100384 a(13)-a(15) from _Donovan Johnson_, Oct 24 2009
%E A100384 Name clarified by _Peter Munn_, Dec 05 2022