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Search: id:A121478
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| A121478 |
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Triangular numbers with three distinct prime factors. |
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+0
3
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| 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; listen)
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OFFSET
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1,1
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EXAMPLE
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11*12/2 = 2*3*11 = 66 is the smalles triangular number with three distinct prime factors, hence a(1) = 66.
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PROGRAM
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(PARI) for(n=1, 100, k=binomial(n+1, 2); if(omega(k)==3, print1(k, ", ")))
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CROSSREFS
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Cf. A000217, A068443, A119663, A121479.
Sequence in context: A036207 A039538 A095751 this_sequence A128896 A109750 A127654
Adjacent sequences: A121475 A121476 A121477 this_sequence A121479 A121480 A121481
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KEYWORD
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easy,nonn
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Aug 01 2006
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