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A196747
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Numbers n such that 3 does not divide swing(n) = A056040(n).
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4
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0, 1, 2, 6, 7, 8, 18, 19, 20, 24, 25, 26, 54, 55, 56, 60, 61, 62, 72, 73, 74, 78, 79, 80, 162, 163, 164, 168, 169, 170, 180, 181, 182, 186, 187, 188, 216, 217, 218, 222, 223, 224, 234, 235, 236, 240, 241, 242, 486, 487, 488, 492, 493, 494, 504, 505, 506, 510
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OFFSET
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1,3
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LINKS
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MAPLE
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SwingExp := proc(m, n) local p, q; p := m;
do q := iquo(n, p);
if (q mod 2) = 1 then RETURN(1) fi;
if q = 0 then RETURN(0) fi;
p := p * m;
od end:
Search := proc(n, L) local m, i, r; m := n;
for i in L do r := SwingExp(i, m);
if r <> 0 then RETURN(NULL) fi
od; n end:
A196747_list := n -> Search(n, [3]): # n is a search limit
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MATHEMATICA
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(* A naive solution *) sf[n_] := n!/Quotient[n, 2]!^2; Select[Range[0, 600], ! Divisible[sf[#], 3] &] (* Jean-François Alcover, Jun 28 2013 *)
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PROG
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(PARI) valp(n, p)=my(s); while(n\=p, s+=n); s
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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