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A158186
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10*n^2 - 7*n + 1.
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3
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1, 4, 27, 70, 133, 216, 319, 442, 585, 748, 931, 1134, 1357, 1600, 1863, 2146, 2449, 2772, 3115, 3478, 3861, 4264, 4687, 5130, 5593, 6076, 6579, 7102, 7645, 8208, 8791, 9394, 10017, 10660, 11323, 12006, 12709, 13432, 14175, 14938, 15721, 16524, 17347
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Sequence found by reading the segment (1, 4) together with the line (one of the diagonal axes) from 4, in the direction 4, 27,..., in the square spiral whose vertices are the generalized heptagonal numbers A085787. - Omar E. Pol, Sep 10 2011
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LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| a(n) = (2*n-1)*(5*n-1).
a(n) = A033571(n) - A008596(n) = A010010(n) - A033571(n).
G.f.: (1+x+18*x^2)/(1-x)^3 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Mar 27 2009]
a(n) = a(n-1)+20*n-17 (with a(0)=1). [From Vincenzo Librandi, Dec 03 2010]
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CROSSREFS
| Sequence in context: A097792 A058067 A175701 * A054412 A122405 A122406
Adjacent sequences: A158183 A158184 A158185 * A158187 A158188 A158189
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KEYWORD
| nonn,easy
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Mar 13 2009
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EXTENSIONS
| Typo in definition corrected by Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 03 2009
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