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 A270650 Min(i, j), where p(i)*p(j) is the n-th term of A006881. 41
 1, 1, 1, 2, 2, 1, 1, 2, 1, 3, 1, 2, 1, 2, 3, 2, 1, 1, 3, 2, 1, 4, 1, 3, 1, 2, 4, 2, 1, 3, 1, 2, 3, 1, 4, 1, 2, 2, 4, 1, 2, 1, 5, 3, 1, 3, 1, 2, 4, 1, 2, 1, 2, 3, 5, 1, 2, 1, 4, 3, 1, 5, 2, 1, 3, 4, 1, 2, 6, 1, 3, 2, 6, 2, 5, 1, 4, 1, 3, 2, 1, 1, 4, 2, 3, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 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)) = (1,1,1,2). 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, A070647, A270652, A270003. Sequence in context: A266499 A226621 A112933 * A088427 A255350 A104482 Adjacent sequences:  A270647 A270648 A270649 * A270651 A270652 A270653 KEYWORD nonn,easy AUTHOR Clark Kimberling, Apr 25 2016 STATUS approved

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Last modified May 16 02:41 EDT 2021. Contains 343937 sequences. (Running on oeis4.)