45 = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
45 = 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1
45 = 0^1 + 1^8 + 2^7 − 3^9 + 4^5 + 5^6 + 6^2 + 7^4 + 8^3 + 9^0
45 = 3^2 + 6^2
45 = (1 + 1) × (11 + 11) + 1
= 2 × 22 + 2/2
= 3 + 3 × 3 + 33
= 44 + 4/4
= 55 − 5 − 5
= 666/6 − 66
= 7 × 7 + 7 − 77/7
= 8 × 8 − 8 − 88/8
= 9 + 9 + 9 + 9 + 9
454 = 14 + 24 + 124 + 244 + 444
45 = binomial(9 + 1, 2) is the 9th triangular number.
Number k such that k^2 + 2 is prime (2027)
Number of ordered pairs of integers (x,y) with x^2+y^2 < 4^2
Numbers k such that (8*10^k + 49)/3 is prime.
Quadruple factorial number n!!!!: a(n) = n*a(n-4), n = 9
Representations, Binary to Hexadecimal:
101101_2
1200_3
231_4
140_5
113_6
63_7
55_8
50_9
41_11
39_12
36_13
33_14
30_15
2d_16
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Undergraduate Texts in Mathematics
Graduate Studies in Mathematics
