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Search: id:A081268
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| 1, 12, 32, 61, 99, 146, 202, 267, 341, 424, 516, 617, 727, 846, 974, 1111, 1257, 1412, 1576, 1749, 1931, 2122, 2322, 2531, 2749, 2976, 3212, 3457, 3711, 3974, 4246, 4527, 4817, 5116, 5424, 5741, 6067, 6402, 6746, 7099, 7461, 7832, 8212, 8601, 8999, 9406
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OFFSET
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0,2
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FORMULA
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a(n)=C(n, 0)+11C(n, 1)+9C(n, 2); binomial transform of (1, 11, 9, 0, 0, 0, .....). a(n)=(9n^2+13n+2)/2. G.f.(1+9x-x^2)/(1-x)^3.
a(n)=9*n+a(n-1)-7 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 10 2009]
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EXAMPLE
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For n=2, a(2)=9*2+1-7=12; n=3, a(3)=9*3+12-7=32; n=4, a(4)=9*4+32-7=61 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 10 2009]
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CROSSREFS
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Cf. A081267.
Sequence in context: A051519 A166959 A134582 this_sequence A068381 A143238 A102080
Adjacent sequences: A081265 A081266 A081267 this_sequence A081269 A081270 A081271
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 15 2003
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