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A081348 First row in maze arrangement of natural numbers. 5
1, 6, 7, 20, 21, 42, 43, 72, 73, 110, 111, 156, 157, 210, 211, 272, 273, 342, 343, 420, 421, 506, 507, 600, 601, 702, 703, 812, 813, 930, 931, 1056, 1057, 1190, 1191, 1332, 1333, 1482, 1483, 1640, 1641, 1806, 1807, 1980, 1981, 2162, 2163, 2352, 2353, 2550 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

FORMULA

a(n) = (2*n^2+4*n+3-(2*n+1)(-1)^n)/2.

a(2*n) = A054569(n).

a(2*n+1) = 2*A014105(n+1).

G.f.: (1+5*x-x^2+3*x^3)/((1-x)^3*(1+x)^2). - Colin Barker, Apr 17 2012

MATHEMATICA

CoefficientList[Series[(1 + 5 x - x^2 + 3 x^3) / ((1 - x)^3 (1 + x)^2), {x, 0, 60}], x] (* Vincenzo Librandi, Aug 08 2013 *)

PROG

(MAGMA) [(2*n^2+4*n+3-(2*n+1)*(-1)^n)/2: n in [0..50]]; // Vincenzo Librandi, Aug 08 2013

CROSSREFS

Cf. A081347, A080335.

Sequence in context: A287760 A210605 A175262 * A002361 A041185 A042389

Adjacent sequences:  A081345 A081346 A081347 * A081349 A081350 A081351

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 19 2003

STATUS

approved

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Last modified February 21 07:18 EST 2018. Contains 299390 sequences. (Running on oeis4.)