A060641 Surround numbers of a length 2n zig-zag.
161, 257, 373, 509, 665, 841, 1037, 1253, 1489, 1745, 2021, 2317, 2633, 2969, 3325, 3701, 4097, 4513, 4949, 5405, 5881, 6377, 6893, 7429, 7985, 8561, 9157, 9773, 10409, 11065, 11741, 12437, 13153, 13889, 14645, 15421, 16217, 17033
Offset: 2
Links
- Harry J. Smith, Table of n, a(n) for n = 2..1000
- E. J. Friedman, Math. Magic
- Index entries for linear recurrences with constant coefficients, signature (3, -3, 1).
Programs
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Mathematica
LinearRecurrence[{3,-3,1},{161,257,373},40] (* or *) Table[10x^2+66x+85,{x,40}] (* Harvey P. Dale, May 26 2013 *) -
PARI
a(n)={10*n^2 + 46*n + 29} \\ Harry J. Smith, Jul 09 2009
Formula
a(n) = 10n^2 + 46n + 29 with n > 1.
From Colin Barker, Apr 22 2012: (Start)
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
G.f.: x^2*(161 - 226*x + 85*x^2)/(1-x)^3. (End)