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A324744
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Number of maximal subsets of {1...n} containing no element whose prime indices all belong to the subset.
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15
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1, 1, 2, 2, 3, 4, 4, 5, 6, 8, 8, 11, 11, 22, 22, 22, 22, 28, 28, 44, 44, 52, 52, 76, 76, 88, 88, 96, 96, 184, 184, 240, 240, 264, 264, 296, 296, 592, 592, 592, 592, 728, 728, 1456, 1456, 1456, 1456, 2912, 2912, 3168, 3168, 3168, 3168, 5568, 5568, 5568, 5568
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OFFSET
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0,3
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COMMENTS
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A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
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LINKS
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EXAMPLE
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The a(1) = 1 through a(8) = 6 maximal subsets:
{1} {1} {2} {1,3} {1,3} {1,3,6} {3,4,6} {1,3,6,7}
{2} {1,3} {2,4} {1,5} {1,5,6} {1,3,6,7} {1,5,6,7}
{3,4} {3,4} {3,4,6} {1,5,6,7} {3,4,6,8}
{2,4,5} {2,4,5,6} {2,4,5,6} {3,6,7,8}
{2,5,6,7} {2,4,5,6,8}
{2,5,6,7,8}
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MATHEMATICA
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maxim[s_]:=Complement[s, Last/@Select[Tuples[s, 2], UnsameQ@@#&&SubsetQ@@#&]];
Table[Length[maxim[Select[Subsets[Range[n]], !MemberQ[#, k_/; SubsetQ[#, PrimePi/@First/@FactorInteger[k]]]&]]], {n, 0, 10}]
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PROG
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(PARI)
pset(n)={my(b=0, f=factor(n)[, 1]); sum(i=1, #f, 1<<(primepi(f[i])))}
a(n)={my(p=vector(n, k, if(k==1, 1, pset(k))), d=0); for(i=1, #p, d=bitor(d, p[i]));
my(ismax(b)=for(k=1, #p, if(!bittest(b, k) && bitnegimply(p[k], b), my(e=bitor(b, 1<<k), f=0); for(j=k+1, #p, if(bittest(b, j) && !bitnegimply(p[j], e), f=1; break)); if(!f, return(0)) )); 1);
my(recurse(k, b)=if(k>#p, ismax(b), my(f=bitnegimply(p[k], b)); if(!f || bittest(d, k), self()(k+1, b)) + if(f, self()(k+1, b+(1<<k)))));
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CROSSREFS
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The non-maximal case is A324738. The case for subsets of {2...n} is A324762.
Cf. A000720, A001462, A007097, A076078, A084422, A085945, A112798, A276625, A290822, A304360, A306844, A320426, A324764.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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