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 A343133 Numbers k such that A064839(k) = A064839(k+1). 0
 1, 9, 58, 61, 73, 80, 82, 1224, 1368, 3075, 3720, 5328, 22112, 45890, 145132, 145138, 269843, 377739, 399281, 622515, 744768, 1280073, 1280437, 1280441, 1281165, 1281190, 1281241, 2961840, 33275384, 54025424, 54161775, 70695344, 91136415, 922135875, 922141772 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The corresponding values of A064839 are 1, 2, 17, 18, 21, 2, 23, 10, 12, 278, 18, 21, 150, 2842, 13434, 13435, 13547, 3654, 33805, 55229, 150, 265608, 265682, 265683, 265832, 265837, 265849, 268, 773172, 308093, 308810, 395158, 540683, 24172493, 24172646, ... Are there numbers k such that A064839(k) = A064839(k+1) = A064839(k+2)? LINKS EXAMPLE 9 is a term since 9 = 3^2 = A001248(2) is the second square of a prime, and 9 + 1 = 10 = 2 * 5 = A006881(2) is the second squarefree semiprime. 58 is a term since 58 = 2*29 = A001248(17) is the 17th squarefree semiprime, and 58 + 1 = 59 = A000040(17) is the 17th prime. MATHEMATICA lpsv = Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {_, _}][[;; , 2]]; lps[n_] := Module[{s = Sort[FactorInteger[n][[;; , 2]]], m}, m = Length[s]; Product[Prime[i]^s[[m - i + 1]], {i, 1, m}]]; n = 100; mx = lpsv[[n]]; c = Table[0, {n}]; v1 = 1; s = {}; Do[lps1 = lps[k]; p = Position[lpsv, lps1][[1, 1]]; c[[p]]++; v2 = c[[p]]; If[v1 == v2, AppendTo[s, k - 1]]; v1 = v2, {k, 2, mx}]; s CROSSREFS Cf. A025487, A064839. Cf. A001248, A006881. Sequence in context: A112616 A197673 A012089 * A044147 A044528 A027174 Adjacent sequences:  A343130 A343131 A343132 * A343134 A343135 A343136 KEYWORD nonn AUTHOR Amiram Eldar, Jul 07 2021 STATUS approved

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Last modified May 19 18:35 EDT 2022. Contains 353847 sequences. (Running on oeis4.)