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A081253 Numbers n such that A081252(m)/m^2 has a local minimum for m = n. 10
2, 4, 9, 18, 37, 74, 149, 298, 597, 1194, 2389, 4778, 9557, 19114, 38229, 76458, 152917, 305834, 611669, 1223338, 2446677, 4893354, 9786709, 19573418, 39146837, 78293674, 156587349, 313174698, 626349397, 1252698794, 2505397589 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The limit of the local minima, lim A081252(n)/n^2 = 1/14. For local maxima cf. A081254.

LINKS

Table of n, a(n) for n=1..31.

Klaus Brockhaus, Illustration for A053646, A081252, A081253 and A081254

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

FORMULA

a(n) = floor(2^n*7/3)

a(n) = a(n-2) + 7*2^(n-2) for n > 1; a(n+2) - a(n) = A005009(n); a(n+1) - a(n) = A062092(n).

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

a(n) = 2*a(n-1) for even n, otherwise a(n) = 2*a(n-1)+1, with a(1)=2. [Bruno Berselli, Jun 19 2014]

EXAMPLE

9 is a term since A081252(8)/8^2 = 5/64 = 0.078, A081252(9)/9^2 = 6/81 = 0.074, A081252(10)/10^2 = 8/100 = 0.080.

CROSSREFS

Cf. A053646, A081252, A081254, A005009, A062092.

Sequence in context: A056185 A152537 A182028 * A118255 A206927 A019299

Adjacent sequences:  A081250 A081251 A081252 * A081254 A081255 A081256

KEYWORD

nonn,easy

AUTHOR

Klaus Brockhaus, Mar 17 2003

STATUS

approved

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Last modified April 18 22:08 EDT 2019. Contains 322237 sequences. (Running on oeis4.)