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Search: id:A014493
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| A014493 |
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Odd triangular numbers. |
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+0
10
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| 1, 3, 15, 21, 45, 55, 91, 105, 153, 171, 231, 253, 325, 351, 435, 465, 561, 595, 703, 741, 861, 903, 1035, 1081, 1225, 1275, 1431, 1485, 1653, 1711, 1891, 1953, 2145, 2211, 2415, 2485, 2701, 2775, 3003, 3081, 3321, 3403, 3655, 3741, 4005, 4095, 4371
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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For n such that n(n+1)/2 is odd see A042963 (congruent to 1 or 2 mod 4).
a(n) = A000217(A042963(n-1)). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 04 2004
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LINKS
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Eric Weisstein's World of Mathematics, Triangular Number
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FORMULA
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Odd numbers of the form n(n+1)/2.
G.f.:x*(-1-x^4-2*x^3-10*x^2-2*x)/((x+1)^2*(x-1)^3) [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009]
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MATHEMATICA
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Select[ Table[n(n + 1)/2, {n, 93}], OddQ[ # ] &] (from Robert G. Wilson v Nov 05 2004).
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CROSSREFS
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Cf. A000217, A014494, A042963.
Sequence in context: A036897 A129966 A110172 this_sequence A147025 A147017 A076825
Adjacent sequences: A014490 A014491 A014492 this_sequence A014494 A014495 A014496
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KEYWORD
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nonn,easy
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AUTHOR
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Mohammad K. Azarian (ma3(AT)evansville.edu)
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EXTENSIONS
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More terms from Erich Friedman (erich.friedman(AT)stetson.edu).
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