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81
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81 is an integer.
Contents
Membership in core sequences
Odd numbers | ..., 75, 77, 79, 81, 83, 85, 87, ... | A005843 |
Composite numbers | ..., 77, 78, 80, 81, 82, 84, 85, ... | A002808 |
Perfect squares | ..., 36, 49, 64, 81, 100, 121, 144, ... | A000290 |
Powers of 3 | 1, 3, 9, 27, 81, 243, 729, 2187, ... | A000244 |
Powers of primes | ..., 71, 73, 79, 81, 83, 89, 97, ... | A000961 |
Fourth powers | 1, 16, 81, 256, 625, 1296, 2401, ... | A000583 |
Quarter-squares | ..., 56, 64, 72, 81, 90, 100, 110, ... | A002620 |
Numbers that are the sum of two squares | ..., 73, 74, 80, 81, 82, 85, 89, ... | A001481 |
Sequences pertaining to 81
Numbers such that string 0, 0 occurs in the base 9 representation of but not of . |
81, 162, 243, 324, 405, 486, 567, 648, 729, 810, 891, ... | A044251 |
sequence beginning at 81 | 81, 244, 122, 61, 184, 92, 46, 23, 70, 35, 106, 53, 160, ... | A008876 |
Partitions of 81
PLACEHOLDER
Roots and powers of 81
In the table below, irrational numbers are given truncated to eight decimal places.
TABLE GOES HERE
Values for number theoretic functions with 81 as an argument
TABLE GOES HERE
Factorization of 81 in some quadratic integer rings
As was mentioned above, 81 is in the square of 3. But it has different factorizations in some quadratic integer rings.
TABLE
REMARKS
Representation of 81 in various bases
Base | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 80 | 15 | 16 | 17 | 18 | 19 | 20 |
Representation | 1010001 | 10000 | 1101 | 311 | 213 | 144 | 121 | 100 | 81 | 74 | 69 | 63 | 5B | 56 | 51 | 4D | 49 | 45 | 41 |
See also
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 |
20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 |
30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 |
40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 |
1729 |