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A084336
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a(n) is the smallest composite number not already in the sequence such that the absolute values of the successive differences are distinct primes.
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0
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4, 6, 9, 14, 21, 8, 25, 36, 55, 12, 35, 64, 27, 58, 99, 10, 57, 110, 39, 98, 15, 76, 143, 16, 95, 22, 119, 18, 121, 228, 49, 158, 45, 176, 315, 32, 169, 20, 171, 328, 51, 214, 33, 200, 391, 24, 217, 44, 243, 46, 273, 34, 245, 468, 85, 314, 63, 296, 537, 28, 285, 548, 69
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OFFSET
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0,1
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COMMENTS
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The absolute values of the successive difference are 2, 3, 5, 7, 13, 17, 11, 19, 43, 23, 29, 37, 31, ...
Does every composite number occur in the sequence? Does every prime occur as a difference?
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LINKS
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MATHEMATICA
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a[0]=4; a[n_] := a[n]=Module[{x, d}, For[x=6, True, x++, If[ !PrimeQ[x]&&PrimeQ[d=Abs[x-a[n-1]]]&&!MemberQ[a/@Range[n-1], x]&&!MemberQ[Table[Abs[a[i+1]-a[i]], {i, 0, n-2}], d], Return[x]]]]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 18 2003
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EXTENSIONS
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STATUS
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approved
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