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 A270652 Max(i,j), where p(i)*p(j) is the n-th term of A006881. 41
 2, 3, 4, 3, 4, 5, 6, 5, 7, 4, 8, 6, 9, 7, 5, 8, 10, 11, 6, 9, 12, 5, 13, 7, 14, 10, 6, 11, 15, 8, 16, 12, 9, 17, 7, 18, 13, 14, 8, 19, 15, 20, 6, 10, 21, 11, 22, 16, 9, 23, 17, 24, 18, 12, 7, 25, 19, 26, 10, 13, 27, 8, 20, 28, 14, 11, 29, 21, 7, 30, 15, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Clark Kimberling, Table of n, a(n) for n = 1..1000 EXAMPLE A006881 = (6, 10, 14, 15, 21, 22, 26, 33, 34, 35, 38, ... ), the increasing sequence of all products of distinct primes.  The first 4 factorizations are 2*3, 2*5, 2*7, 3*5, so that (a(1), a(2), a(3), a(4)) = (2,3,4,3). MATHEMATICA mx = 350; t = Sort@Flatten@Table[Prime[n]*Prime[m], {n, Log[2, mx/3]}, {m, n + 1, PrimePi[mx/Prime[n]]}]; (* A006881, Robert G. Wilson v, Feb 07 2012 *) u = Table[FactorInteger[t[[k]]][[1]], {k, 1, Length[t]}]; u1 = Table[u[[k]][[1]], {k, 1, Length[t]}]  (* A096916 *) PrimePi[u1]  (* A270650 *) v = Table[FactorInteger[t[[k]]][[2]], {k, 1, Length[t]}]; v1 = Table[v[[k]][[1]], {k, 1, Length[t]}]  (* A070647 *) PrimePi[v1]  (* A270652 *) d = v1 - u1  (* A176881 *) Map[PrimePi[FactorInteger[#][[-1, 1]]] &, Select[Range@ 240, And[SquareFreeQ@ #, PrimeOmega@ # == 2] &]] (* Michael De Vlieger, Apr 25 2016 *) CROSSREFS Cf. A000040, A006881, A096916, A270650, A070647, A270003. Sequence in context: A123066 A330239 A235121 * A326693 A280242 A325953 Adjacent sequences:  A270649 A270650 A270651 * A270653 A270654 A270655 KEYWORD nonn,easy AUTHOR Clark Kimberling, Apr 25 2016 STATUS approved

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Last modified June 16 04:56 EDT 2021. Contains 345056 sequences. (Running on oeis4.)