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 A000469 1 together with products of 2 or more distinct primes. 30
 1, 6, 10, 14, 15, 21, 22, 26, 30, 33, 34, 35, 38, 39, 42, 46, 51, 55, 57, 58, 62, 65, 66, 69, 70, 74, 77, 78, 82, 85, 86, 87, 91, 93, 94, 95, 102, 105, 106, 110, 111, 114, 115, 118, 119, 122, 123, 129, 130, 133, 134, 138, 141, 142, 143, 145, 146, 154, 155, 158 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Nonprime squarefree numbers. Except for 1, composite n such that the squarefree part of n is greater than phi(n). - Benoit Cloitre, Apr 06 2002 LINKS T. D. Noe, Table of n, a(n) for n = 1..10000 FORMULA n such that A007913(n)>A000010(n). - Benoit Cloitre, Apr 06 2002 N-floor(N/p1) - floor(N/(p2) - ... - floor(N/p(i) + floor(N/(c2) + floor(N/(c3)+ ... + floor(N/c(j)-1 where N is any number; p1,p2 are the primes with p(i) being the first prime > square root of N and c2, c3 are the numbers other than 1 in this sequence with c(j) <= N will yield the number of primes less than or equal to N other than p1, p2, ..., p(i). - Ben Paul Thurston, Aug 15 2007 A005171(a(n))*A008966(a(n)) = 1. - Reinhard Zumkeller, Nov 01 2009 Sum(n=1, Infinity, 1/a(n)^s) = Zeta(s)/Zeta(2s) - PrimeZeta(s). - Enrique Pérez Herrero, Mar 31 2012 n such that A001221(n) = A001222(n), n nonprime. - Carlos Eduardo Olivieri, Aug 06 2015 MAPLE select(numtheory:-issqrfree and not isprime, [\$1..1000]); # Robert Israel, Aug 06 2015 MATHEMATICA lst={}; Do[If[SquareFreeQ[n], If[ !PrimeQ[n], AppendTo[lst, n]]], {n, 200}]; lst (* Vladimir Joseph Stephan Orlovsky, Jan 20 2009 *) With[{upto=200}, Complement[Select[Range[upto], SquareFreeQ], Prime[ Range[ PrimePi[ upto]]]]] (* Harvey P. Dale, Oct 01 2011 *) Select[Range[200], !PrimeQ[#] && PrimeOmega[#] == PrimeNu[#] &] (* Carlos Eduardo Olivieri, Aug 06 2015 *) PROG (PARI) for(n=0, 64, if(isprime(n), n+1, if(issquarefree(n), print(n)))) (PARI) for(n=1, 160, if(core(n)*(1-isprime(n))>eulerphi(n), print1(n, ", "))) (Haskell) a000469 n = a000469_list !! (n-1) a000469_list = filter ((== 0) . a010051) a005117_list -- Reinhard Zumkeller, Mar 21 2014 CROSSREFS Cf. A005117, A007913, A000010, A010051, A239508, A239509, A120944 (composite squarefree numbers, same sequence apart from the first term). Sequence in context: A182853 A212168 A080365 * A120944 A327829 A052053 Adjacent sequences:  A000466 A000467 A000468 * A000470 A000471 A000472 KEYWORD nonn,easy,nice AUTHOR Dan Bentley (dtb(AT)research.att.com) STATUS approved

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Last modified October 18 10:50 EDT 2019. Contains 328147 sequences. (Running on oeis4.)