

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
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OFFSET

1,2


LINKS

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


FORMULA

a(n) = floor((12n3)/7).
From Chai Wah Wu, Sep 11 2018: (Start)
a(n) = a(n1) + a(n7)  a(n8) 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



