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 A080684 Number of 13-smooth numbers <= n. 1
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 16, 17, 17, 18, 19, 20, 20, 21, 22, 23, 24, 25, 25, 26, 26, 27, 28, 28, 29, 30, 30, 30, 31, 32, 32, 33, 33, 34, 35, 35, 35, 36, 37, 38, 38, 39, 39, 40, 41, 42, 42, 42, 42, 43, 43, 43, 44, 45, 46, 47, 47, 47, 47, 48, 48, 49 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Range = primes 2 to 13. Input pn=13 in script below. Code below is much faster than the code for cross-reference. For input of n=200 13 times as fast and many times faster for larger input of n. LINKS Harvey P. Dale, Table of n, a(n) for n = 1..1000 MATHEMATICA Accumulate[Table[If[Max[FactorInteger[n][[All, 1]]]<14, 1, 0], {n, 80}]] (* Harvey P. Dale, Jul 23 2018 *) PROG (PARI) smoothn(n, pn) = { for(m=1, n, pr=1; forprime(p=2, pn, pr*=p; ); ct=1; for(x=1, m, f=0; forprime(y=nextprime(pn+1), floor(x), if(x%y == 0, f=1; break) ); if(gcd(x, pr)<>1, if(f==0, ct+=1; )) ); print1(ct", "); ) } CROSSREFS Cf. A071520, A051038. Sequence in context: A309083 A106618 A320113 * A159062 A301274 A093616 Adjacent sequences:  A080681 A080682 A080683 * A080685 A080686 A080687 KEYWORD easy,nonn AUTHOR Cino Hilliard, Mar 02 2003 STATUS approved

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Last modified April 9 17:48 EDT 2020. Contains 333361 sequences. (Running on oeis4.)