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A051724 Numerator of n/12. 25
0, 1, 1, 1, 1, 5, 1, 7, 2, 3, 5, 11, 1, 13, 7, 5, 4, 17, 3, 19, 5, 7, 11, 23, 2, 25, 13, 9, 7, 29, 5, 31, 8, 11, 17, 35, 3, 37, 19, 13, 10, 41, 7, 43, 11, 15, 23, 47, 4, 49, 25, 17, 13, 53, 9, 55, 14, 19, 29, 59, 5, 61, 31, 21, 16, 65, 11, 67, 17, 23, 35, 71 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

COMMENTS

Or, numerator of n/(n+12).

Multiplicative with a(2^e) = 2^max(0, e-2), a(3^e) = 3^max(0,e-1), a(p^e) = p^e otherwise. - David W. Wilson, Jun 12 2005

Arises in the equal-tempered musical scale - see Goldstein (1977), Table 1. - N. J. A. Sloane, Aug 29 2018

A strong divisibility sequence: gcd(a(n),a(m)) = a(gcd(n,m)) for n, m >= 1. - Peter Bala, Feb 24 2019

REFERENCES

R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 269.

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 0..10000

P. Bala, A note on the sequence of numerators of a rational function

A. A. Goldstein, Optimal temperament, SIAM Review 19.3 (1977): 554-562.

FORMULA

a(n) = n/gcd(n, 12). - David W. Wilson, Jun 12 2005

From R. J. Mathar, Apr 18 2011: (Start)

a(n) = A109053(n)/12.

Dirichlet g.f.: zeta(s-1)*(1 - 2/3^s - 1/2^s + 2/6^s - 1/4^s + 2/12^s). (End)

From Peter Bala, Feb 24 2019: (Start)

a(n) = n/gcd(n,12) is a quasi-polynomial in n since gcd(n,12) is a purely periodic sequence of period 12.

O.g.f.: F(x) - F(x^2) - 2*F(x^3) - F(x^4) + 2*F(x^6) + 2*F(x^12), where F(x) = x/(1 - x)^2.

O.g.f. for reciprocals: Sum_{n >= 1} x^n/a(n) = Sum_{d divides 12} (phi(d)/d) * log(1/(1 - x^d)) = log(1/(1 - x)) + (1/2)*log(1/(1 - x^2)) + (2/3)*log(1/(1 - x^3)) + (2/4)*log(1/(1 - x^4)) + (2/6)*log(1/(1 - x^6)) + (4/12)*log(1/(1 - x^12)), where phi(n) denotes the Euler totient function A000010. (End)

MAPLE

seq(numer(n/12), n=0..100); # Nathaniel Johnston, Apr 18 2011

MATHEMATICA

f[n_]:=Numerator[n/(n+12)]; Array[f, 100, 0] (* Vladimir Joseph Stephan Orlovsky, Feb 17 2011*)

PROG

(Sage) [lcm(n, 12)/12 for n in xrange(0, 72)] # Zerinvary Lajos, Jun 09 2009

(MAGMA) [Numerator(n/12): n in [0..100]]; // Vincenzo Librandi, Apr 18 2011

(PARI) a(n) = numerator(n/12); \\ Michel Marcus, Aug 19 2018

(GAP) List([0..80], n->NumeratorRat(n/12)); # Muniru A Asiru, Feb 24 2019

CROSSREFS

Cf. A109053. Cf. Sequences given by the formula numerator(n/(n + k)): A026741 (k = 2), A051176 (k = 3), A060819 (k = 4), A060791 (k = 5), A060789 (k = 6), A106608 thru A106612 (k = 7 thru 11), A106614 thru A106621 (k = 13 thru 20).

Sequence in context: A319684 A102778 A135544 * A084303 A011508 A195429

Adjacent sequences:  A051721 A051722 A051723 * A051725 A051726 A051727

KEYWORD

nonn,easy,frac,mult

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified December 6 18:03 EST 2019. Contains 329809 sequences. (Running on oeis4.)