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A037227 If n = 2^m*k, k odd, then a(n) = 2*m+1. 12
1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 9, 1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 11, 1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 9, 1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 13, 1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 9, 1, 3, 1, 5, 1, 3, 1, 7, 1, 3, 1, 5, 1, 3, 1, 11, 1, 3, 1, 5, 1, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(A005408(n)) = 1; a(A016825(n)) = 3; A017113(a(n)) = 5; A051062(a(n)) = 7. - Reinhard Zumkeller, Jun 30 2012

Take the number of rightmost zeros in the binary expansion of n, double it, and increment it by 1. - Ralf Stephan, Aug 22 2013

Gives the maximum possible number of n X n complex Hermitian matrices with the property that all of their nonzero real linear combinations are nonsingular (see Adams et al. reference). - Nathaniel Johnston, Dec 11 2013

LINKS

T. D. Noe, Table of n, a(n) for n=1..1024

J. F. Adams, P. D. Lax, and R. S. Phillips, On matrices whose real linear combinations are nonsingular, Proceedings of the American Mathematical Society, 16:318-322, 1965.

D. B. Shapiro, Problem 10456: Anticommuting Matrices, Amer. Math. Monthly, 105 (1998), 565-566.

Index entries for sequences related to binary expansion of n

FORMULA

a(n) = Sum_{d divides n} (-1)^(d+1)*mu(d)*tau(n/d). Multiplicative with a(p^e) = 2*e+1 if p = 2; 1 if p > 2. - Vladeta Jovovic, Apr 27 2003

a(n) = a(n-1)+(-1)^n*(a(floor(n/2))+1). - Vladeta Jovovic, Apr 27 2003

a(2*n) = a(n) + 2, a(2*n+1) = 1. a(n) = 2*A007814(n) + 1. - Ralf Stephan, Oct 07 2003

a((2*n-1)*2^p)  = 2*p+1, p  >= 0 and n >= 1. - Johannes W. Meijer, Feb 07 2013

From _Peter Bala, Feb 07 2016: (Start)

a(n) = ( A002487(n-1) + A002487(n+1) )/A002487(n).

a(n*2^(k+1) + 2^k) = 2*k + 1 for n,k >= 0; thus a(2*n+1) = 1, a(4*n+2) = 3, a(8*n+4) = 5, a(16*n+8) = 7 and so on. Note the square array ( n*2^(k+1) + 2^k - 1 )n, k>=0 is the transpose of A075300.

G.f. Sum_{n >= 0} (2*n + 1)*x^(2^n)/(1 - x^(2^(n+1))). (End)

a(n) = 2*floor(A002487(n-1)/A002487(n))+1 for n > 1. - I. V. Serov, Jun 15 2017

MAPLE

nmax:=102: for p from 0 to ceil(simplify(log[2](nmax))) do for n from 1 to ceil(nmax/(p+2)) do a((2*n-1)*2^p):= 2*p+1: od: od: seq(a(n), n=1..nmax);  # Johannes W. Meijer, Feb 07 2013

MATHEMATICA

a[n_] := Sum[(-1)^(d+1)*MoebiusMu[d]*DivisorSigma[0, n/d], {d, Divisors[n]}]; Table[a[n], {n, 1, 102}] (* Jean-Fran├žois Alcover, Dec 31 2012, after Vladeta Jovovic *)

PROG

(Haskell)

a037227 = (+ 1) . (* 2) . a007814  -- Reinhard Zumkeller, Jun 30 2012

(R)

maxrow <- 6 # by choice

a <- 1

for(m in 0:maxrow){

for(k in 0:(2^m-1)) {

   a[2^(m+1)    +k] <- a[2^m+k]

   a[2^(m+1)+2^m+k] <- a[2^m+k]

}

   a[2^(m+1)      ] <- a[2^(m+1)] + 2

}

a

# Yosu Yurramendi, May 21 2015

(PARI) a(n)=2*valuation(n, 2)+1 \\ Charles R Greathouse IV, May 21 2015

CROSSREFS

Cf. A001511, A002487, A007814, A075300, A220466.

Sequence in context: A134700 A085407 A016475 * A056753 A243158 A154723

Adjacent sequences:  A037224 A037225 A037226 * A037228 A037229 A037230

KEYWORD

nonn,easy,nice,mult

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Erich Friedman

STATUS

approved

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Last modified September 23 17:50 EDT 2017. Contains 292363 sequences.