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Search: id:A081950
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| A081950 |
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Smallest triangular number k such that k-1 has exactly n (not necessarily distinct) prime factors. |
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+0
2
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| 3, 10, 21, 55, 253, 325, 1081, 4753, 8001, 18145, 226801, 293761, 7378561, 1181953, 33566721, 184291201, 471905281, 75479041, 924908545, 4831985665, 8590131201, 137438167041, 146163916801, 1051224625153, 309236465665, 19791199862785
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(4) = 2*3*3*3+1 = 55.
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CROSSREFS
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Cf. A081951.
Sequence in context: A007687 A006308 A008837 this_sequence A071563 A139116 A120109
Adjacent sequences: A081947 A081948 A081949 this_sequence A081951 A081952 A081953
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 02 2003
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EXTENSIONS
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Extended and edited by Ryan Propper (rpropper(AT)stanford.edu), Jun 21 2005
a(24)-a(26) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 31 2009
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