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Search: id:A052180
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| A052180 |
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Last filtering prime for n-th prime p: find smallest prime factor of each of the composite numbers between p and next prime; take maximal value. |
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24
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| 2, 2, 3, 2, 3, 2, 3, 5, 2, 5, 3, 2, 3, 7, 5, 2, 5, 3, 2, 7, 3, 5, 7, 3, 2, 3, 2, 3, 11, 3, 7, 2, 11, 2, 5, 7, 3, 13, 5, 2, 11, 2, 3, 2, 11, 13, 3, 2, 3, 5, 2, 13, 11, 7, 5, 2, 5, 3, 2, 17, 13, 3, 2, 3, 17, 5, 11, 2, 3, 5, 19, 7, 13, 3, 5, 17, 3, 13, 7, 2, 7, 2, 19, 3, 5, 11, 3, 2, 3, 11, 13, 3, 17
(list; graph; listen)
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OFFSET
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2,1
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LINKS
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T. D. Noe, Table of n, a(n) for n=2..10000
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FORMULA
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a(n)=Max[{A020639[j], j=1+p[n], ..., p[n+1]-1}= Max[{Min{p|p divides j}, j=1+p[n], ..., p[n+1]-1}=
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EXAMPLE
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For n=9, n-th prime is 23, composites between 23 and next prime are 24 25 26 27 28, smallest prime divisors are 2 5 2 3 2; maximal value is 5, so a(9)=5.
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MATHEMATICA
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ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] mi[x_] := Min[ba[x]] Table[Max[Table[mi[ba[w]], {w, Prime[j]+1, -1+Prime[j+1]}]], {j, 1, 256}]
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CROSSREFS
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Cf. A052248, A020639, A000720, A083269, A000879.
Sequence in context: A099427 A059964 A087458 this_sequence A065151 A073093 A088873
Adjacent sequences: A052177 A052178 A052179 this_sequence A052181 A052182 A052183
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KEYWORD
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nonn,easy,nice
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AUTHOR
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Labos, E. (labos(AT)ana.sote.hu), Feb 05 2000
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