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 A351867 Heptagonal numbers (or 7-gonal numbers) which are products of four distinct primes. 0
 3010, 4774, 10465, 14326, 20566, 28462, 54538, 59059, 59830, 66178, 66994, 87142, 104755, 112042, 120670, 121771, 131905, 137710, 138886, 168610, 179158, 201214, 212722, 223054, 249166, 273406, 288490, 290191, 314530, 343546, 358534, 375778, 401401, 405418, 419635, 461605 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A squarefree subsequence of heptagonal numbers. LINKS Table of n, a(n) for n=1..36. EXAMPLE 3010 = 2*5*7*43 = 35(5*35-3)/2. 4774 = 2*7*11*31 = 44(5*44-3)/2. 10465 = 5*7*13*23 = 65(5*65-3)/2. 14326 = 2*13*19*29 = 76(5*76-3)/2. PROG (Python) from itertools import count, islice from sympy import factorint def A351867_gen(): return filter(lambda k:sum((f := factorint(k)).values()) == 4 == len(f), (n*(5*n-3)//2 for n in count(1))) A351867_list = list(islice(A351867_gen(), 20)) # Chai Wah Wu, Apr 14 2022 CROSSREFS Cf. A000566, A046386. Sequence in context: A279584 A004228 A004229 * A004230 A162606 A233963 Adjacent sequences: A351864 A351865 A351866 * A351868 A351869 A351870 KEYWORD nonn AUTHOR Massimo Kofler, Apr 12 2022 STATUS approved

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Last modified July 15 21:59 EDT 2024. Contains 374334 sequences. (Running on oeis4.)