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A007924
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The number n written using the greedy algorithm in the base where the values of the places are 1 and primes.
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9
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0, 1, 10, 100, 101, 1000, 1001, 10000, 10001, 10010, 10100, 100000, 100001, 1000000, 1000001, 1000010, 1000100, 10000000, 10000001, 100000000, 100000001, 100000010, 100000100, 1000000000, 1000000001, 1000000010, 1000000100, 1000000101
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OFFSET
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0,3
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COMMENTS
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Any nonnegative number can be written as a sum of distinct primes + e, where e is 0 or 1.
Terms contain only digits 0 and 1.
Without the "greedy" condition there is ambiguity - for example 5 = 3+2 has two representations.
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REFERENCES
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S. S. Pillai, "An arithmetical function concerning primes", Annamalai University Journal (1930), pp. 159-167.
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LINKS
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FORMULA
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a(n) is the binary representation of b(n) = 2^pi(n) + b(n-p(pi(n))) for n > 0 and a(0) = b(0)= 0, where pi(k) = number of primes <= k (A000720) and p(k) = k-th prime (A008578). - Frank Ellermann, Dec 18 2001
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EXAMPLE
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4 = 3 + 1, so a(4) = 101.
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MATHEMATICA
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cprime[n_Integer] := (If[n==0, 1, Prime[n]]); gentable[n_Integer] := (m=n; ptable={}; While[m!=0, (i=0; While[cprime[i]<=m, i++]; j=0; While[j<i, AppendTo[ptable, 0]; j++]; ptable[[i]]=1; m=m-cprime[i-1])]; ptable); decimal[n_Integer] := (gentable[n]; Sum[2^(k-1)*ptable[[k]], {k, 1, Length[ptable]}]); Table[IntegerString[decimal[n], 2], {n, 0, 100}](* Frank M Jackson, Jan 06 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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R. Muller
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EXTENSIONS
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STATUS
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approved
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