\( \sqrt{81} = 8 + 1 \)
1 / 81 = 0.012345679012345679012345679....
81 = 1 + 2 + 3 + 45 + 6 + 7 + 8 + 9
81 = 9 + 8 + 7 + 6 + 5 + 43 + 2 + 1
81 = 0^8 − 1^9 + 2^6 − 3^7 + 4^5 + 5^4 + 6^2 + 7^1 + 8^3 + 9^0
1 = (11 − 1 − 1)(1+1)
= (2 + 2/2)(2+2)
= 3 × 33
= (4 − 4/4)4
= 5 × 5 + 55 + 5/5
= 6 − 66 + 6 × 66/6
= 77/7 − 7 + 77
= 88 − 8 + 8/8
= 9 × 9
a(n) = 3*n*(n + 3)/2. (n = 6)
Number of fractions in Farey series of order 16: 0/1, 1/16, 1/15, 1/14, 1/13, 1/12, 1/11, 1/10, 1/9, 1/8, 2/15, 1/7, 2/13, 1/6, 2/11, 3/16, 1/5, 3/14, 2/9, 3/13, 1/4, 4/15, 3/11, 2/7, 3/10, 4/13, 5/16, 1/3, 5/14, 4/11, 3/8, 5/13, 2/5, 5/12, 3/7, 7/16, 4/9, 5/11, 6/13, 7/15, 1/2, 8/15, 7/13, 6/11, 5/9, 9/16, 4/7, 7/12, 3/5, 8/13, 5/8, 7/11, 9/14, 2/3, 11/16, 9/13, 7/10, 5/7, 8/11, 11/15, 3/4, 10/13, 7/9, 11/14, 4/5, 13/16, 9/11, 5/6, 11/13, 6/7, 13/15, 7/8, 8/9, 9/10, 10/11, 11/12, 12/13, 13/14, 14/15, 15/16, 1/1
Number of points of norm <= 5^2 in square lattice.
Number k such that k^2 + 2 is prime
Moser-de Bruijn sequence: sums of distinct powers of 4
Number k such that the Woodall number kx2^k - 1 is prime
Representations, Binary to Hexadecimal:
1010001_2
10000_3
1101_4
311_5
213_6
144_7
121_8
100_9
74_11
69_12
63_13
5b_14
56_15
51_16
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Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
