Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A heptagonal pyramidal number is the sum of the first few heptagonal numbers. The heptagonal number for n can be calculated by adding up the heptagonal numbers for 1 to n, or by using the formula n(n + 1)(5n 2)/6. The first few heptagonal pyramidal numbers are: 1, 8, 26, 60, 115, 196, 308, 456, 645, 880, 1166, 1508, 1911, 2380, 2920, 3536, 4233, 5016, 5890, 6860, 7931, 9108 (sequence A002413 in OEIS)
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