OFFSET
1,1
COMMENTS
Each of a(n), a(n)-1, a(n)-2, a(n)-3, a(n)+1, a(n)+2, a(n)+3 has at least one square divisor.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A077640(n) + 3. - Amiram Eldar, Feb 09 2021
EXAMPLE
217073=17*113^2, 217073-1=2^4*13567, 217073-2=3^2*89*271, 217073-3=2*5*7^2*443, 217073+1=2*3*11^2*13*23, 217073+2=5^2*19*457, 217073+3=2^2*54269.
MATHEMATICA
Select[Range[200000, 5000000], !SquareFreeQ[#] &&!SquareFreeQ[#-1] &&!SquareFreeQ[#+1] &&!SquareFreeQ[#-2] &&!SquareFreeQ[#+2] &&!SquareFreeQ[#-3] &&!SquareFreeQ[#+3]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Mar 29 2011
EXTENSIONS
More terms from Carl Najafi, Aug 22 2011
STATUS
approved