七角数
七角数（ななかくすう、Heptagonal number）とは、多角数の一種で、正七角形の形に点を並べたとき、図に含まれる点の総数にあたる自然数である。七角数は無数にあり、そのなかでは1が最も小さい。"n"番目の七角数は以下の式によって表すことができる。
:formula_1
七角数を小さいものから列挙すると次のようになる。
:1, 7, 18, 34, 55, 81, 112, 148, 189, 235, 286, 342, 403, 469, 540, 616, 697, 783, 874, 970, …（）
Q836270
多角数
Concept
Q188866
正七角形
Concept
Q21199
自然数
Concept
Q199
1
Concept
Q199
1
Concept
Q23350
7
Concept
Q38712
18
Concept
Q712639
34
Concept
Q686819
55
Concept
Q712876
81
Concept
Q716846
112
Concept
Q284807
148
Concept
Q280959
189
Concept
Q857163
235
Concept
Q277761
286
Concept
Q1095904
342
Concept
Q1490794
403
Concept
Q225995
469
Concept
Q579979
540
Concept
Q1069927
616
Concept
Q967999
七角数
Concept
Q967999
七角数
Concept
Q967999
七角数
Concept
Q967999
七角数
Concept
2020-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1
DATE
2020-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1
DATE
2020-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
1
DATE
2020-07-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
7
DATE
2018-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
18
DATE
2034-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
34
DATE
2055-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
55
DATE
1981-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
81
DATE
2011-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
11
DATE
2020-02-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
2
DATE
2014-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
14
DATE
2020-08-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
8
DATE
2018-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
18
DATE
2020-09-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
9
DATE
2023-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
23
DATE
2020-05-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
5
DATE
2028-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
28
DATE
2020-06-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
6
DATE
2034-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
34
DATE
2020-02-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
2
DATE
2040-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
40
DATE
2020-03-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
3
DATE
2046-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
46
DATE
2020-09-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
9
DATE
2054-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
54
DATE
2061-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
61
DATE
2020-06-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
6
DATE
1969-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
69
DATE
2020-07-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
7
DATE
1978-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
78
DATE
2020-03-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
3
DATE
1987-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
87
DATE
2020-04-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
4
DATE
1997-01-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
97
DATE
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
subclass of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
instance of
subclass of
subclass of
subclass of