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A369238 Tetraprime numbers differing by more than 3 from any other squarefree number. 0
72474, 106674, 193026, 237522, 261478, 308649, 342066, 370785, 391674, 491322, 604878, 865974, 885477, 931022, 938598, 1005630, 1070727, 1152822, 1186926, 1206822, 1289978, 1306878, 1363326, 1371774, 1392726, 1412918, 1455249, 1528111, 1634227, 1654678, 1688478 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Tetraprimes are the product of four distinct prime numbers (cf. A046386).
LINKS
EXAMPLE
72474 = 2 * 3 * 47 * 257 is a tetraprime; 72471 = 3 * 7^2 * 17 * 29, 72472 = 2^3 * 9059, 72473 = 23^2 * 137, 72475 = 5^2 * 13 * 223, 72476 = 2^2 * 18119, 72477 = 3^2 * 8053 are all nonsquarefree numbers, so 72474 is a term.
MATHEMATICA
f[n_] := Module[{e = FactorInteger[n][[;; , 2]], p}, p = Times @@ e; If[p > 1, 0, If[e == {1, 1, 1, 1}, 1, -1]]]; SequencePosition[Array[f, 2*10^6], {0, 0, 0, 1, 0, 0, 0}][[;; , 1]] + 3 (* Amiram Eldar, Jan 19 2024 *)
CROSSREFS
Cf. A046386, A013929. Subsequence of A268332.
Sequence in context: A126658 A251340 A183788 * A093212 A114258 A238151
KEYWORD
nonn
AUTHOR
Massimo Kofler, Jan 19 2024
STATUS
approved

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Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)