login
Positions where A119842 is zero.
5

%I #10 Mar 03 2016 02:24:42

%S 6,10,14,15,21,22,24,26,30,33,34,35,38,39,40,42,46,51,54,55,56,57,58,

%T 60,62,65,66,69,70,74,77,78,82,84,85,86,87,88,90,91,93,94,95,96,102,

%U 104,105,106,110,111,114,115,118,119,122,123,126,129,130,132,133,134

%N Positions where A119842 is zero.

%C In addition to the terms of A119899 includes also terms with prime signature p*q*r, e.g. 30 (= 2*3*5). Anything else?

%H Alois P. Heinz, <a href="/A119847/b119847.txt">Table of n, a(n) for n = 1..6677</a>

%t b[s_, t_] := b[s, t] = If[Length[s] < 1, 1, Sum[If[Mod[PrimeOmega[x], 2] == 1 - t && Length[Select[s, Mod[#, x] == 0 &]] == 1, b[s~Complement~{x}, 1 - t], 0], {x, s}]]; c[n_] := Module[{l, m}, l = Sort[FactorInteger[n], #1[[2]] > #2[[2]] &]; m = Product[Prime[i]^l[[i]][[2]], {i, 1, Length[l]} ]; b[Divisors[m][[2 ;; -2]], Mod[PrimeOmega[m], 2]]]; A119847 = Position[ Table[c[n], {n, 1, 200}], 0] // Flatten (* _Jean-François Alcover_, Mar 03 2016, after _Alois P. Heinz_ *)

%Y Complement: A119848. Superset of A119899. Cf. A119850.

%Y Cf. A229153.

%K nonn

%O 1,1

%A _Antti Karttunen_, Jun 04 2006