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A081031 Positions of white keys on piano keyboard, start with A0 = the 1st key. 3
1, 3, 4, 6, 8, 9, 11, 13, 15, 16, 18, 20, 21, 23, 25, 27, 28, 30, 32, 33, 35, 37, 39, 40, 42, 44, 45, 47, 49, 51, 52, 54, 56, 57, 59, 61, 63, 64, 66, 68, 69, 71, 73, 75, 76, 78, 80, 81, 83, 85, 87, 88 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..52.

FORMULA

a(n) = floor((12n-3)/7).

From Chai Wah Wu, Sep 11 2018: (Start)

a(n) = a(n-1) + a(n-7) - a(n-8) for n > 8.

G.f. for a keyboard with infinite number of keys: x*(x^7 + 2*x^6 + x^5 + 2*x^4 + 2*x^3 + x^2 + 2*x + 1)/(x^8 - x^7 - x + 1). (End)

a(n) = A060107(n) + 1 for 1 <= n <= 36. - Jianing Song, Oct 14 2019

EXAMPLE

First, 3rd, 4th, 6th, etc. keys of piano keyboard are white.

MATHEMATICA

Join[{1, 3}, Flatten[Table[12n+{4, 6, 8, 9, 11, 13, 15}, {n, 0, 6}]], {88}] (* Harvey P. Dale, Mar 15 2013 *)

CROSSREFS

Cf. A059620, A081032, A060107.

Sequence in context: A061402 A047206 A187474 * A285681 A133280 A280762

Adjacent sequences:  A081028 A081029 A081030 * A081032 A081033 A081034

KEYWORD

fini,full,nonn

AUTHOR

David W. Wilson, Mar 02 2003

STATUS

approved

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Last modified November 12 09:01 EST 2019. Contains 329052 sequences. (Running on oeis4.)