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21, 87, 197, 351, 549, 791, 1077, 1407, 1781, 2199, 2661, 3167, 3717, 4311, 4949, 5631, 6357, 7127, 7941, 8799, 9701, 10647, 11637, 12671, 13749, 14871, 16037, 17247, 18501, 19799, 21141, 22527, 23957, 25431, 26949, 28511, 30117, 31767
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (22*n^2-1)^2 - (121*n^2-11)*(2*n)^2 = 1 can be written as a(n)^2 - A158539(n)*A005843(n)^2 =1.
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: x*(-21-24*x+x^2)/(x-1)^3.
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MATHEMATICA
| 22Range[40]^2-1 (* or *) LinearRecurrence[{3, -3, 1}, {21, 87, 197}, 40]
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PROG
| MAGMA) I:=[21, 87, 197]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 14 2012
(PARI) for(n=1, 40, print1(22*n^2 - 1", ")); \\ Vincenzo Librandi, Feb 14 2012
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CROSSREFS
| Cf. A005843, A158539.
Sequence in context: A063651 A045016 A171129 * A020248 A203173 A194532
Adjacent sequences: A158537 A158538 A158539 * A158541 A158542 A158543
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KEYWORD
| nonn,easy,changed
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 21 2009
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EXTENSIONS
| Comment rewritten - R. J. Mathar, Oct 16 2009
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