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 A161554 Denominators of sequence of fractions of primes that minimize absolute value of difference between the fractions and 1/4. 1
 3, 5, 7, 11, 13, 13, 19, 19, 29, 29, 29, 29, 43, 43, 53, 53, 53, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 67, 149, 149, 149, 163, 163, 173, 173, 173, 173, 173, 173, 173, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 269, 269, 269, 269 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For n = 2, there are two primes available for use in numerator or denominator: 2,3. The best approximation to 1/4 is 2/3. Sequence begins at n = 2. LINKS EXAMPLE For n=2, there are two primes available to approximate 1/4. The closest fraction in absolute value is 2/3. The first few approximating fractions are: 2/3, 2/5, 2/7, 3/11, 3/13,... PROG (PARI) afr(n) = {kdiff = 1; fp = primes(n); for (i=1, n, num = fp[i]; for (j=1, n, den = fp[j]; diff = abs(num/den - 1/4); if (diff <= kdiff, kdiff = diff; knum = num; kden = den; ); ); ); return(knum/kden); } a(n) = denominator(afr(n)); \\ Michel Marcus, Jun 12 2013 & Mar 21 2016 CROSSREFS Cf. A161555 (numerators). Sequence in context: A114235 A285848 A086527 * A245644 A070087 A100933 Adjacent sequences:  A161551 A161552 A161553 * A161555 A161556 A161557 KEYWORD nonn,frac AUTHOR Daniel Tisdale, Jun 13 2009 EXTENSIONS More terms from Michel Marcus, Jun 12 2013 STATUS approved

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Last modified December 11 10:48 EST 2018. Contains 318049 sequences. (Running on oeis4.)