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A178320 INVERT transform of A008805 (triangular numbers with repeats). 0
1, 2, 6, 14, 35, 85, 208, 508, 1241, 3032, 7407, 18096, 44209, 108005, 263861, 644625, 1574849, 3847430, 9399452, 22963302, 56100424, 137055967, 334834156, 818015548, 1998450352, 4882307945, 11927707309, 29139948412, 71190260748 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..28.

N. J. A. Sloane, Transforms

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

FORMULA

G.f.: -1/(x^5-x^4-2*x^3+2*x^2+2*x-1).

EXAMPLE

a(3) = 14 = (3, 3, 1, 1) * (1, 1, 2, 6) = (3 + 3 + 2 + 6).

MAPLE

b:= proc(n) local m;

  m:= ceil((n+1)/2);

  m*(m+1)/2

end:

invtr:= proc(b)

  local a;

  a:= proc(n) option remember; local i;

        `if`(n<1, 1, add(a(n-i) *b(i-1), i=1..n+1))

  end;

end:

a:= invtr(b):

seq(a(n), n=0..30);

CROSSREFS

Cf. A008805.

Sequence in context: A269506 A292816 A105635 * A297187 A231509 A318018

Adjacent sequences:  A178317 A178318 A178319 * A178321 A178322 A178323

KEYWORD

nonn,easy

AUTHOR

Gary W. Adamson, Dec 21 2010

EXTENSIONS

Edited by Alois P. Heinz, Dec 25 2010

STATUS

approved

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Last modified October 29 20:41 EDT 2020. Contains 338073 sequences. (Running on oeis4.)