A177899 Nonsquarefree numbers that are not in A177880.

8, 16, 24, 27, 40, 48, 54, 56, 80, 81, 88, 104, 112, 120, 125, 135, 136, 152, 162, 168, 176, 184, 189, 208, 216, 232, 240, 248, 250, 264, 270, 272, 280, 296, 297, 304, 312, 328, 336, 343, 344, 351, 368, 375, 376, 378, 405, 408, 424, 432, 440, 456, 459, 464, 472, 488, 496, 512, 513, 520, 528, 536

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

Let B(x) be the counting function for terms not exceeding x. Then for x tends to infinity, B(x)=C*x+o(x^(0.5+eps), where C = Product_{i=p^(3^k) with prime p and k>=0}(1-1/(i^2+i+1)) - 1/zeta(2).

Maple

isA005836 := proc(n) convert(convert(n, base, 3), set) intersect {2} ; % = {} ; end proc:
isA177880 := proc(n) local f; for f in ifactors(n)[2]  do if not isA005836(op(2, f)) then return true; end if;  end do: return false; end proc:
isA177899 := proc(n) not numtheory[issqrfree](n) and not isA177880(n) ; end proc:
for n from 1 to 1000 do if isA177899(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Dec 20 2010

Mathematica

Select[Range[500], AnyTrue[(e = FactorInteger[#][[;; , 2]]), #1 > 1 &] && AllTrue[e, DigitCount[#1, 3, 2] == 0 &] &] (* Amiram Eldar, Aug 31 2020 *)

Crossrefs

Cf. A013929, A177880.

Sequence in context: A345193 A365866 A033859 * A358727 A246311 A344538

Adjacent sequences: A177896 A177897 A177898 * A177900 A177901 A177902

Keyword

nonn

Author

Vladimir Shevelev, Dec 15 2010

Status

approved