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A059406
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a(n) = a(n-1)*(3a(n-1)+1)/2 with a(1) = 1.
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1
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OFFSET
| 1,2
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COMMENTS
| a(1) = 1, a(n+1) = sum of a(n) numbers beginning with a(n) + 1: a(2) = 2, a(3) = 3+4 = 7, a(4) = 8+9+...13+14 = 77. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 07 2005
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,12
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FORMULA
| a(n) = A007501(n)/3 = A005449(a(n-1)) - Henry Bottomley (se16(AT)btinternet.com), Oct 03 2001
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EXAMPLE
| a(3) = 7 so a(4) = 7*(3*7+1)/2 = 7*22/2 = 77
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MATHEMATICA
| f[n_Integer] := n(3n + 1)/2; NestList[f, 2, 8]
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PROG
| (PARI) { a=2/3; for (n = 1, 12, write("b059406.txt", n, " ", a=a*(3*a + 1)/2); ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jun 26 2009]
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CROSSREFS
| Cf. A000326.
Sequence in context: A083455 A083829 A067963 * A042791 A128293 A071409
Adjacent sequences: A059403 A059404 A059405 * A059407 A059408 A059409
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 29 2001
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