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A193868 Even central polygonal numbers. 4
2, 4, 16, 22, 46, 56, 92, 106, 154, 172, 232, 254, 326, 352, 436, 466, 562, 596, 704, 742, 862, 904, 1036, 1082, 1226, 1276, 1432, 1486, 1654, 1712, 1892, 1954, 2146, 2212, 2416, 2486, 2702, 2776, 3004, 3082, 3322, 3404, 3656, 3742, 4006, 4096, 4372 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Odd triangular numbers plus 1.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Index to sequences with linear recurrences with constant coefficients, signature (1,2,-2,-1,1)

FORMULA

a(n) = A000124(A042963(n-1)).

a(n) = 1 + A014493(n).

a(n) = 2*A174114(n).

G.f. -2*x*(1+x+4*x^2+x^3+x^4) / ( (1+x)^2*(x-1)^3 ). - R. J. Mathar, Aug 25 2011

PROG

(MAGMA) [1+((2*n-1)*(2*n-1-(-1)^n)/2): n in [1..50]]; // Vincenzo Librandi, Aug 18 2011

CROSSREFS

Cf. A000124, A193867.

Sequence in context: A242205 A192150 A049441 * A059622 A131475 A239363

Adjacent sequences:  A193865 A193866 A193867 * A193869 A193870 A193871

KEYWORD

nonn,easy

AUTHOR

Omar E. Pol, Aug 15 2011

STATUS

approved

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Last modified December 21 23:06 EST 2014. Contains 252326 sequences.