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Interval information
Ratio 21/13
Factorization 3 × 7 × 13-1
Monzo [0 1 0 1 0 -1
Size in cents 830.25325¢
Name tridecimal supraminor sixth
Color name thuzo 6th, 3uz6
FJS name [math]\text{M6}^{7}_{13}[/math]
Special properties reduced
Tenney height (log2 nd) 8.09276
Weil height (log2 max(n, d)) 8.78463
Wilson height (sopfr (nd)) 23
Harmonic entropy
(Shannon, [math]\sqrt{nd}[/math])
~4.2186 bits

[sound info]
open this interval in xen-calc

21/13, the tridecimal supraminor sixth, is ca. 830 cents in size. It has a very good approximation in 13edo.

This interval is a ratio of two consecutive Fibonacci numbers, therefore it approximates the golden ratio, specifically acoustic phi. In this case, 21/13 is ~2.8 ¢ flat of the golden ratio.

See also