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 A121478 Triangular numbers with three distinct prime factors. 2
 66, 78, 105, 120, 190, 231, 276, 300, 378, 406, 435, 465, 528, 561, 595, 666, 741, 820, 861, 903, 946, 1035, 1128, 1176, 1275, 1378, 1485, 1653, 1953, 2016, 2080, 2211, 2278, 2485, 2556, 2628, 2775, 3081, 3160, 3240, 3655, 3741, 3916, 4005, 4371, 4465 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 11*12/2 = 2*3*11 = 66 is the smalles triangular number with three distinct prime factors, hence a(1) = 66. PROG (PARI) for(n=1, 100, k=binomial(n+1, 2); if(omega(k)==3, print1(k, ", "))) CROSSREFS Cf. A000217, A068443, A119663, A121479. Sequence in context: A036207 A039538 A095751 * A330809 A128896 A109750 Adjacent sequences:  A121475 A121476 A121477 * A121479 A121480 A121481 KEYWORD easy,nonn AUTHOR Klaus Brockhaus, Aug 01 2006 STATUS approved

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Last modified September 22 15:04 EDT 2021. Contains 347607 sequences. (Running on oeis4.)