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A363830
Lesser of 2 successive sphenic numbers (k, k+4) sandwiching 3 consecutive nonsquarefree numbers.
0
602, 1374, 2274, 2522, 3122, 3282, 4202, 4922, 4958, 4974, 5822, 5885, 6874, 7298, 7674, 9062, 9422, 9474, 10322, 11222, 12590, 13074, 15531, 15722, 16818, 18766, 19131, 19745, 20447, 21535, 22922, 24774, 24938, 25323, 25622, 26522, 26738, 27978, 28034, 28074, 28222
OFFSET
1,1
EXAMPLE
602 = 2 * 7 * 43 and 606 = 2 * 3 * 101 are sphenic numbers; 603 = 3^2 * 67, 604 = 2^2 * 151 and 605 = 5 * 11^2 are 3 consecutive nonsquarefree numbers, so 602 is a term.
1374 = 2 * 3 * 229 and 1378 = 2 * 13 * 53 are sphenic numbers; 1375 = 5^3 * 11, 1376 = 2^5 * 43 and 1377 = 3^4 * 17 are 3 consecutive nonsquarefree numbers, so 1374 is a term.
MATHEMATICA
Select[Partition[Select[Range[30000], FactorInteger[#][[;; , 2]] == {1, 1, 1} &], 2, 1], Differences[#] == {4} && ! Or @@ SquareFreeQ /@ Range[First[#] + 1, Last[#] - 1] &][[;; , 1]] (* Amiram Eldar, Oct 19 2023 *)
CROSSREFS
Sequence in context: A045940 A124057 A252435 * A045941 A268588 A251462
KEYWORD
nonn
AUTHOR
Massimo Kofler, Oct 19 2023
STATUS
approved