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Search: id:A081950
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A081950 Smallest triangular number k such that k-1 has exactly n (not necessarily distinct) prime factors. +0
2
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)
OFFSET

1,1

EXAMPLE

a(4) = 2*3*3*3+1 = 55.

CROSSREFS

Cf. A081951.

Sequence in context: A007687 A006308 A008837 this_sequence A071563 A139116 A120109

Adjacent sequences: A081947 A081948 A081949 this_sequence A081951 A081952 A081953

KEYWORD

nonn

AUTHOR

Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 02 2003

EXTENSIONS

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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Last modified December 20 13:50 EST 2009. Contains 171054 sequences.


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