OFFSET
1,1
COMMENTS
The complementary sequence, squarefree part of n is one greater than the square part of n, is A069187.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
Antonio Roldán, hojaynumeros.blogspot.com
FORMULA
EXAMPLE
1260 = 2^2*3^2*5*7, square part: 2^2*3^2 = 36, squarefree part: 5*7 = 35, and 36 = 35+1.
MAPLE
b:= proc() 1 end:
a:= proc(n) option remember; local i, k;
if n>1 then a(n-1) fi;
for k from b(n-1)+1 while 1<>mul(i[2], i=ifactors(k^2-1)[2])
do od; b(n):=k; k^4-k^2
end:
seq(a(n), n=1..50); # Alois P. Heinz, Apr 29 2011
MATHEMATICA
okQ[n_] := Module[{p, e, sfp}, {p, e} = Transpose[FactorInteger[n]]; e = Mod[e, 2]; sfp = Times @@ (p^e); n/sfp - sfp == 1]; Select[Range[10^5], okQ] (* T. D. Noe, Apr 29 2011 *)
PROG
(PARI) for(n=1, 1e3, if(issquarefree(n^2-1), print1(n^4-n^2", "))) \\ Charles R Greathouse IV, Apr 29, 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Apr 29 2011
STATUS
approved