The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 Table of n, a(n) for n=1..31. 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 Adjacent sequences: A369235 A369236 A369237 * A369239 A369240 A369241 KEYWORD nonn AUTHOR Massimo Kofler, Jan 19 2024 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

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