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A081346 First column in maze arrangement of natural numbers A081344. 3
1, 2, 9, 10, 25, 26, 49, 50, 81, 82, 121, 122, 169, 170, 225, 226, 289, 290, 361, 362, 441, 442, 529, 530, 625, 626, 729, 730, 841, 842, 961, 962, 1089, 1090, 1225, 1226, 1369, 1370, 1521, 1522, 1681, 1682, 1849, 1850, 2025, 2026, 2209, 2210, 2401, 2402, 2601 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Interleaves odd squares A016754 with central polygonal numbers A001844.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

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

FORMULA

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

a(2*n)=A016754(n), a(2*n+1)=2*A001844(n).

G.f.: (1+x+5*x^2-x^3+2*x^4)/((1-x)^3*(1+x)^2). [Colin Barker, Sep 03 2012]

PROG

(MAGMA) [n^2+n+1+n*(-1)^n: n in [0..50]]; // Vincenzo Librandi, Sep 05 2011

CROSSREFS

Cf. A081345.

Sequence in context: A005695 A079747 A191576 * A290592 A058551 A119183

Adjacent sequences:  A081343 A081344 A081345 * A081347 A081348 A081349

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Mar 19 2003

STATUS

approved

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Last modified February 25 00:39 EST 2018. Contains 299630 sequences. (Running on oeis4.)