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A125176 Row sums of A125175. 5
1, 3, 7, 14, 28, 56, 112, 224, 448, 896, 1792, 3584, 7168, 14336, 28672, 57344, 114688, 229376, 458752, 917504, 1835008, 3670016, 7340032, 14680064, 29360128, 58720256, 117440512, 234881024, 469762048, 939524096, 1879048192, 3758096384, 7516192768, 15032385536 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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

FORMULA

a(1) = 1, a(2) = 3, a(n) = 7*2^(n-3) for n>=3.

From Colin Barker, Oct 12 2013: (Start)

a(n) = 2*a(n-1) for n>3.

G.f.: x*(1 + x + x^2)/(1-2*x). (End)

E.g.f.: (7*Exp(2*x) - 7 - 6*x - 2*x^2)/8. - G. C. Greubel, Jun 05 2019

EXAMPLE

First few rows of A125175 are:

  1;

  1, 2;

  1, 3, 3;

  1, 4, 5, 4; ....

a(4) = 1 + 4 + 5 + 4 = 14.

a(6) = 1 + 6 + 14 + 20 + 9 + 6 = 56 = 7*8 = 7*2^3.

MATHEMATICA

Rest@CoefficientList[Series[x*(1+x+x^2)/(1-2*x), {x, 0, 40}], x] (* Vincenzo Librandi, Oct 12 2013 *)

PROG

(PARI) concat([1, 3], vector(30, n, 7*2^(n-1))) \\ G. C. Greubel, Jun 05 2019

(MAGMA) [1, 3] cat [7*2^(n-3): n in [3..40]];  // G. C. Greubel, Jun 05 2019

(Sage) [1, 3]+[7*2^(n-3) for n in (3..40)] # G. C. Greubel, Jun 05 2019

(GAP) Concatenation([1, 3], List([3..40], n-> 7*2^(n-3))) # G. C. Greubel, Jun 05 2019

CROSSREFS

Cf. A125175.

Essentially identical to A005009.

Sequence in context: A140741 A088209 A089074 * A153234 A293334 A266625

Adjacent sequences:  A125173 A125174 A125175 * A125177 A125178 A125179

KEYWORD

nonn,easy

AUTHOR

Gary W. Adamson, Nov 22 2006

EXTENSIONS

More terms from N. J. A. Sloane, Dec 15 2007

STATUS

approved

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Last modified October 18 18:56 EDT 2019. Contains 328197 sequences. (Running on oeis4.)