A093505 - OEIS

A093505

a(n) = floor(A001969(n)/2 + 1/2).

0, 2, 3, 3, 5, 5, 6, 8, 9, 9, 10, 12, 12, 14, 15, 15, 17, 17, 18, 20, 20, 22, 23, 23, 24, 26, 27, 27, 29, 29, 30, 32, 33, 33, 34, 36, 36, 38, 39, 39, 40, 42, 43, 43, 45, 45, 46, 48, 48, 50, 51, 51, 53, 53, 54, 56, 57, 57, 58, 60, 60, 62, 63, 63, 65

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OFFSET

1,2

COMMENTS

The sequence is a quasi-inverse of A161560: For n >= 2, a(A161560(n+1)+1) = n or n-1. - Jaroslav Krizek, Jun 13 2009, corrected Jul 13 2012

Conjecture: Essentially partial sums of A036577 (true for at least 10000 terms). - Sean A. Irvine, Jul 17 2022

LINKS

Table of n, a(n) for n=1..65.

FORMULA

a(n) = A001969(n) - n + 1 for n >= 2. - Jaroslav Krizek, Jun 13 2009

EXAMPLE

a(5) = 5 because the fifth evil number = 9 and floor(9/2 + 1/2) = 5.

PROG

(PARI) a(n)=(2*n+hammingweight(n-1)%2-1)\2 \\ Charles R Greathouse IV, Mar 22 2013

CROSSREFS

Cf. A001969, A000069, A036577.

Sequence in context: A010761 A320840 A161172 * A238527 A146071 A167411

Adjacent sequences: A093502 A093503 A093504 * A093506 A093507 A093508

KEYWORD

easy,nonn

AUTHOR

Michael Joseph Halm, May 13 2004

EXTENSIONS

Corrected and edited by Jaroslav Krizek, Jun 13 2009

STATUS

approved