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Search: id:A076551
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| A076551 |
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Smallest triangular number with n prime factors (counted without multiplicity). |
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+0
8
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| 1, 3, 6, 66, 210, 3570, 103740, 930930, 56812470, 1722580860, 32395433070, 265257422430, 91348974206490, 8923863379851420, 330196858581850260, 14193386885746698630, 2378522762792139793830, 351206814022419685159830
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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a(0) = 1 because 1 is a triangular number with zero prime factors; a(3) = 66 because 66 = 2*3*11 is a triangular number with 3 distinct prime factors.
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PROGRAM
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(PARI) {n=12; v=vector(n); for(k=1, 1000000, t=k*(k+1)/2; d=1+omega(t); if(d<=n&&v[d]<1, v[d]=t)); for(j=1, n, print1(v[j], ", "))}
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CROSSREFS
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Cf. A000217.
Sequence in context: A137091 A137135 A069077 this_sequence A127637 A068665 A050722
Adjacent sequences: A076548 A076549 A076550 this_sequence A076552 A076553 A076554
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KEYWORD
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nonn
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AUTHOR
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Shyam Sunder Gupta (guptass(AT)rediffmail.com), Oct 19 2002
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EXTENSIONS
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a(12) from Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 31 2003
a(13) from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Aug 02 2006
a(14)-a(16) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 28 2009
a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Feb 07 2009
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