OFFSET
1,1
LINKS
Christopher E. Thompson, Table of n, a(n) for n = 1..1000
MAPLE
SF:= select(numtheory:-issqrfree, [$1..10^6]):
SF[select(i -> SF[i]-SF[i-1]>=4 and SF[i+1]-SF[i]>=4, [$2..nops(SF)-1])]; # Robert Israel, Feb 02 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Christopher E. Thompson, Feb 01 2016
STATUS
approved