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A084336 a(n) is the smallest composite number not already in the sequence such that the absolute values of the successive differences are distinct primes. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
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?
LINKS
MATHEMATICA
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]]]]
CROSSREFS
Sequence in context: A310673 A171664 A286303 * A094750 A241013 A330071
KEYWORD
nonn
AUTHOR
Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 18 2003
EXTENSIONS
Edited by Dean Hickerson, Jun 30 2003
STATUS
approved

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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)