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A343578
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a(n) = 32*n^2 - 40*n + 10.
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0
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2, 58, 178, 362, 610, 922, 1298, 1738, 2242, 2810, 3442, 4138, 4898, 5722, 6610, 7562, 8578, 9658, 10802, 12010, 13282, 14618, 16018, 17482, 19010, 20602, 22258, 23978, 25762, 27610, 29522, 31498, 33538, 35642, 37810, 40042, 42338, 44698, 47122, 49610, 52162, 54778, 57458
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OFFSET
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1,1
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COMMENTS
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a(n) is the sum of cross multiplying integers in groups of 4, a(n) = (4n-4)*(4n-1) + (4n-3)*(4n-2). For example, the group 4,5,6,7 yields the sum 4*7 + 5*6 = 58 = a(2).
Sequence found by reading the line from 2, in the direction 2, 58, ..., in the square spiral whose vertices are the generalized 18-gonal numbers A274979. - Omar E. Pol, Apr 20 2021
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LINKS
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FORMULA
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a(n) = determinant(matrix[4*n-1, -4*n+2, 4*n-3, 4*n-4]). - Peter Luschny, Apr 24 2021
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MATHEMATICA
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CROSSREFS
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Cf. A274979 (generalized 18-gonal numbers).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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