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A100384
a(n) = the smallest number x >= 2 such that for m = x to x + n - 1, A006530(m) increases.
5
2, 2, 8, 8, 90, 168, 9352, 46189, 721970, 721970, 6449639, 565062156, 11336460025, 37151747513, 256994754033
OFFSET
1,1
COMMENTS
A006530(m) is the largest prime factor of m.
a(16) > 3*10^11. - Donovan Johnson, Oct 24 2009
a(16) > 10^13. - Giovanni Resta, Jul 25 2013
EXAMPLE
a(5)=90 because the largest prime factors of 90,91,92,93,94 are 5,13,23,31,47.
PROG
(Python)
from sympy import factorint
def A100384(n):
k, a = 2, [max(factorint(m+2)) for m in range(n)]
while True:
for i in range(1, n):
if a[i-1] >= a[i]:
break
else:
return k
a = a[i:] + [max(factorint(k+j+n)) for j in range(i)]
k += i # Chai Wah Wu, Jul 24 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Dec 09 2004
EXTENSIONS
Edited by Don Reble, Jun 13 2007
a(13)-a(15) from Donovan Johnson, Oct 24 2009
Name clarified by Peter Munn, Dec 05 2022
STATUS
approved