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A076551 Smallest triangular number with n prime factors (counted without multiplicity). 11
1, 3, 6, 66, 210, 3570, 103740, 930930, 56812470, 1722580860, 32395433070, 265257422430, 91348974206490, 8923863379851420, 330196858581850260, 14193386885746698630, 2378522762792139793830, 351206814022419685159830, 28791787439593010836313310 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
a(19) <= 8285055066500101241048306610. a(20) <= 120052594044654305809137933570. - Donovan Johnson, Feb 28 2012
LINKS
EXAMPLE
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.
PROG
(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], ", "))}
CROSSREFS
Sequence in context: A069077 A214838 A225789 * A127637 A306451 A068665
KEYWORD
nonn
AUTHOR
Shyam Sunder Gupta, Oct 19 2002
EXTENSIONS
a(12) from Rick L. Shepherd, May 31 2003
a(13) from Klaus Brockhaus, Aug 02 2006
a(14)-a(16) from Donovan Johnson, Jan 28 2009
a(17) from Donovan Johnson, Feb 07 2009
a(18) from Donovan Johnson, Feb 28 2012
STATUS
approved

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Last modified April 22 20:16 EDT 2024. Contains 371906 sequences. (Running on oeis4.)