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A120353
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Sum of 5 consecutive powers of 3, starting with a power of 9..
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2
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121, 1089, 9801, 88209, 793881, 7144929, 64304361, 578739249, 5208653241, 46877879169, 421900912521, 3797108212689, 34173973914201, 307565765227809, 2768091887050281, 24912826983452529, 224215442851072761, 2017938985659654849, 18161450870936893641
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Always a square.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..300
Tanya Khovanova, Recursive Sequences
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FORMULA
| a(n) = 121*3^(2n-2)
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EXAMPLE
| a(2) = 3^2+3^3+3^4+3^5+3^6 = 121*(3^2) = 1089
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MATHEMATICA
| Total/@Select[Partition[3^Range[0, 60], 5, 1], IntegerQ[Log[9, First[#]]]&] (* or *) Table[121 3^(2n-2), {n, 30}] (* From Harvey P. Dale, May 03 2011 *)
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PROG
| (MAGMA) [121*3^(2*n-2): n in [1..30]]; // Vincenzo Librandi, Jun 10 2011
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CROSSREFS
| Sequence in context: A141350 A190877 A203959 * A175983 A036928 A088171
Adjacent sequences: A120350 A120351 A120352 * A120354 A120355 A120356
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KEYWORD
| nonn
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AUTHOR
| Anton Joha (antonjoha(AT)hotmail.com), Jun 25 2006
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EXTENSIONS
| Corrected and extended by Harvey P. Dale, May 03 2011.
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