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A157870
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a(n) = (4n+1)(4n+2) = (4n+2)!/(4n)!.
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2
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2, 30, 90, 182, 306, 462, 650, 870, 1122, 1406, 1722, 2070, 2450, 2862, 3306, 3782, 4290, 4830, 5402, 6006, 6642, 7310, 8010, 8742, 9506, 10302, 11130, 11990, 12882, 13806, 14762, 15750, 16770, 17822, 18906, 20022, 21170, 22350, 23562, 24806, 26082, 27390, 28730, 30102, 31506, 32942
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| I was trying to prove the irrationality of pi and I encountered this sequence.
A014634 * 2 = A157870. A157870 / 2 = A014634. [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 10 2009]
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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)=A002378(4n+1)=2*A014634(n). [R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 11 2009]
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MATHEMATICA
| lst={}; Do[a=(2*n+1)*(4*n+1)*2; AppendTo[lst, a], {n, 0, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 10 2009]
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CROSSREFS
| Sequence in context: A189100 A085637 A193177 * A078838 A089288 A154413
Adjacent sequences: A157867 A157868 A157869 * A157871 A157872 A157873
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KEYWORD
| nonn,easy
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AUTHOR
| SUNKU Sai Swaroop (sai2020(AT)gmail.com), Mar 08 2009
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EXTENSIONS
| Corrected definition and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 11 2009
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