OFFSET
1,2
EXAMPLE
a(6)=11 because 1,2,3,4,5,6,8,9,10,15,16 are the non-isolated divisors of 720.
MAPLE
with(numtheory): A:=proc(n) local div, NID, i: div:=divisors(factorial(n)): NID:={}: for i to tau(factorial(n)) do if member(div[i]-1, div)=true or member(div[i]+1, div)=true then NID:= `union`(NID, {div[i]}) else end if end do: NID end proc: seq(nops(A(n)), n=1..30); # Emeric Deutsch, Oct 12 2007
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Sep 30 2007
EXTENSIONS
Corrected and extended by Emeric Deutsch, Oct 12 2007
a(31)-a(35) from Ray Chandler, May 28 2008
a(36)-a(50) from Ray Chandler, Jun 20 2008
a(51)-a(56) from Lucas A. Brown, Oct 02 2024
STATUS
approved