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A137281
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Numbers n such that T(n) is not divisible by T(i), 1<i<n, where T(n)=nth triangular number A000217.
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3
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2, 4, 7, 10, 13, 16, 22, 25, 28, 31, 34, 37, 43, 46, 49, 52, 58, 61, 67, 70, 73, 76, 82, 85, 88, 94, 97, 103, 106, 118, 121, 127, 130, 133, 136, 142, 145, 148, 151, 157, 163, 166, 169, 172, 178, 187, 190, 193, 196, 202, 205, 208, 211, 214, 217, 226, 229, 232, 238, 241
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| T. D. Noe, Table of n, a(n) for n = 1..1000
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FORMULA
| n such that A076982(n) = 2. - T. D. Noe, Apr 12 2011
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EXAMPLE
| T(4)=10 is not divisible by lesser T's 3, 6;
T(7)=28 is not divisible by lesser T's 3, 6, 10, 15, 21.
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MATHEMATICA
| nn = 241; tri = Table[n*(n+1)/2, {n, nn}]; Select[Range[2, nn], ! MemberQ[Mod[tri[[#]], Take[tri, {2, # - 1}]], 0] &] (* T. D. Noe, Apr 12 2011 *)
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CROSSREFS
| Cf. A000217.
Sequence in context: A194228 A194236 A127762 * A003067 A130243 A061465
Adjacent sequences: A137278 A137279 A137280 * A137282 A137283 A137284
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Mar 14 2008
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