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A045765
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n - d(n) never takes these values, where d(n) = A000005(n).
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27
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7, 8, 13, 19, 20, 24, 25, 28, 33, 36, 37, 40, 43, 49, 50, 52, 55, 56, 63, 64, 66, 67, 68, 74, 75, 79, 85, 88, 98, 100, 103, 108, 109, 112, 113, 116, 117, 123, 124, 126, 131, 132, 133, 134, 136, 140, 143, 145, 150, 153, 156, 159, 160, 163, 164, 167, 168
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OFFSET
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1,1
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COMMENTS
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Since A000005(x) <= 1 + x/2, n is in the sequence if there are no x <= 2*(n+1) with n = x - d(x). - Robert Israel, Oct 12 2015
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LINKS
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MAPLE
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N:= 1000: # to get all terms <= N
sort(convert({$1..N} minus {seq(x - numtheory:-tau(x), x=1..2*(1+N))}, list)); # Robert Israel, Oct 12 2015
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MATHEMATICA
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lim = 10000; Take[Complement[Range@ lim, Sort@ DeleteDuplicates@ Table[n - DivisorSigma[0, n], {n, lim}]], 57] (* Michael De Vlieger, Oct 13 2015 *)
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PROG
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(PARI)
allocatemem((2^31)+(2^30));
v060990 = vector(uplim);
for(n=3, uplim, v060990[n-numdiv(n)]++);
A060990 = n -> if(!n, 2, v060990[n]);
uplim2 = 36756720;
n=0; k=1; while(n <= uplim2, if(0==A060990(n), write("b045765_big.txt", k, " ", n); k++); n++; );
(Scheme)
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CROSSREFS
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Cf. A000005, A002183, A049820, A060990, A070319, A236562, A236565, A261100, A262511, A262686, A262901, A262902, A262903, A262909, A263081.
Cf. A259934 (gives the infinite trunk of the same tree, conjectured to be unique).
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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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