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 A102615 Nonprime numbers of order 2. 16
 1, 8, 10, 14, 15, 16, 20, 22, 24, 25, 27, 30, 32, 33, 35, 36, 38, 39, 40, 44, 46, 48, 49, 50, 51, 54, 55, 56, 58, 62, 63, 64, 66, 68, 69, 70, 72, 75, 76, 77, 78, 80, 82, 85, 86, 87, 88, 90, 92, 93, 94, 96, 99, 100, 102, 104, 105, 108, 110, 111, 114, 115, 116, 117, 118, 120 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS nps(n,0) -> list nonprime(n) or the sequence of nonprime numbers. nps(n,1) -> list nonprime(nonprime(n)) or nps of order 1 nps(n,2) -> list nonprime(nonprime(nonprime(n))) or nps of order 2 ..... The order is the number of nestings - 1. We avoid the nestings in the script with a loop. Nonprimes (A018252) with nonprime (A018252) subscripts. a(n) U A078782(n) = A018252(n), a(n+1) U A175250(n) = A018252(n) for n >= 1. a(n) = nonprime(nonprime(n)) = A018252(A018252(n)). a(4) = 14 because a(4) = b(b(4)) = b(8) = 14, b = nonprime. a(1) = 1, a(n) = nonprimes (A018252) with composite (A002808) subscripts for n >=2. [Jaroslav Krizek, Mar 13 2010] LINKS EXAMPLE Nonprime(2) = 4. Nonprime(4) = 8 the second entry. MAPLE # For Maple code for the prime/nonprime compound sequences (listed in cross-references) see A003622.  - N. J. A. Sloane, Mar 30 2016 MATHEMATICA nonPrime[n_] := FixedPoint[n + PrimePi[ # ] &, n]; Nest[nonPrime, Range, 2] (* Robert G. Wilson v, Feb 04 2005 *) PROG (PARI) \We perform nesting(s) with a loop. cics(n, m) = { local(x, y, z); for(x=1, n, z=x; for(y=1, m+1, z=composite(z); ); print1(z", ") ) } composite(n) = \ The n-th composite number. 1 is defined as a composite number. { local(c, x); c=1; x=0; while(c <= n, x++; if(!isprime(x), c++); ); return(x) } CROSSREFS Cf. A018252. Let A = primes A000040, B = nonprimes A018252. The 2-level compounds are AA = A006450, AB = A007821, BA = A078782, BB = A102615. The 3-level compounds AAA, AAB, ..., BBB are A038580, A049078, A270792, A102617, A270794, A270796, A102216. Sequence in context: A101764 A309065 A048591 * A308874 A030490 A076639 Adjacent sequences:  A102612 A102613 A102614 * A102616 A102617 A102618 KEYWORD nonn AUTHOR Cino Hilliard, Jan 31 2005 EXTENSIONS Edited by Robert G. Wilson v, Feb 04 2005 STATUS approved

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Last modified November 19 22:34 EST 2019. Contains 329323 sequences. (Running on oeis4.)