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A166402
Composite terms of sequence A166401.
3
4, 8, 9, 16, 18, 25, 27, 32, 36, 49, 50, 64, 75, 81, 98, 100, 121, 125, 128, 144, 147, 162, 169, 196, 200, 225, 242, 243, 245, 256, 289, 324, 338, 343, 361, 363, 392, 400, 441, 484, 507, 512, 529, 576, 578, 605, 625, 676, 722, 729, 784, 841, 845, 847, 867, 882
OFFSET
1,1
COMMENTS
Sequence A166401 contains 1 and all the primes in addition to this sequence's terms. For those terms that are not powers of primes, see A166403.
LINKS
MAPLE
filter:= proc(n) local a, b;
if isprime(n) then return false fi;
if issqr(n) then return true fi;
a, b:= selectremove(t -> (t^2 <= n), numtheory:-divisors(n));
min(b) mod max(a) = 0
end proc:
select(filter, [$4..1000]); # Robert Israel, Jan 13 2016
MATHEMATICA
Select[Range[2, 900], ! PrimeQ[#] && Divisible[(d = Divisors[#])[[n = Floor[Length[d]/2 + 1]]], d[[-n]]] &] (* Ivan Neretin, Jan 12 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Oct 13 2009
EXTENSIONS
More terms from Max Alekseyev, Feb 21 2010
STATUS
approved