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A349539 Smallest number m in a set of at least three consecutive triangular numbers with three distinct prime factors. 1
378, 406, 528, 820, 861, 1953, 2485, 3081, 5050, 5151, 5778, 7750, 9316, 11026, 11175, 18145, 19306, 19503, 36046, 36315, 39621, 92665, 93096, 130816, 131328, 135981, 205120, 326836, 337431, 661825, 816003, 1439056, 1993006, 1995003, 2166321, 2835771 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(1) = 378 because 378 is the smallest number in the first set of three consecutive triangular numbers with three distinct prime factors, i.e., (378 = 2*3^3*7, 406 = 2*7*29, 435 = 3*5*29).
MATHEMATICA
t[n_] := n*(n + 1)/2; q[n_] := PrimeNu[n] == 3; Select[Partition[t /@ Range[3*10^3], 3, 1], AllTrue[#, q] &][[;; , 1]] (* Amiram Eldar, Nov 26 2021 *)
CROSSREFS
Sequence in context: A003918 A350183 A045197 * A098835 A134602 A268373
KEYWORD
nonn
AUTHOR
Shyam Sunder Gupta, Nov 25 2021
EXTENSIONS
Name clarified by Michel Marcus, Dec 02 2021
STATUS
approved

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Last modified April 12 06:13 EDT 2024. Contains 371623 sequences. (Running on oeis4.)