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A014637 Odd heptagonal numbers (A000566). 4
1, 7, 55, 81, 189, 235, 403, 469, 697, 783, 1071, 1177, 1525, 1651, 2059, 2205, 2673, 2839, 3367, 3553, 4141, 4347, 4995, 5221, 5929, 6175, 6943, 7209, 8037, 8323, 9211, 9517, 10465, 10791, 11799, 12145, 13213, 13579, 14707, 15093, 16281, 16687, 17935 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..42.

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

FORMULA

G.f.:(1+13*x^4+14*x^3+46*x^2+6*x)/((1+x)^2*(1-x)^3) [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009]

From Ant King, Sep 01 2011: (Start)

a(n) = (1/8)*(1+(-1)^n+4*n)*(-1+5*(-1)^n+20*n)

a(n) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5)

a(n) = 80+2*a(n-2)-a(n-4)

(End)

MATHEMATICA

Table[1/8 (1+(-1)^n+4 n) (-1+5 (-1)^n+20 n), {n, 0, 42}] (* Ant King, Sep 01 2011 *)

PROG

(PARI) a(n)=(5*(-1)^n+20*n-1)*(4*n+1+(-1)^n)/8 \\ Charles R Greathouse IV, Sep 01 2011

CROSSREFS

Cf. A000566, A014640, A014773, A014792.

Sequence in context: A203878 A043077 A192718 * A062212 A272864 A121183

Adjacent sequences:  A014634 A014635 A014636 * A014638 A014639 A014640

KEYWORD

nonn,easy

AUTHOR

Mohammad K. Azarian

EXTENSIONS

Extended and description corrected by Patrick De Geest

STATUS

approved

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Last modified May 24 03:52 EDT 2016. Contains 273236 sequences.