The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A034729 a(n) = Sum_{ k, k|n } 2^(k-1). 43
1, 3, 5, 11, 17, 39, 65, 139, 261, 531, 1025, 2095, 4097, 8259, 16405, 32907, 65537, 131367, 262145, 524827, 1048645, 2098179, 4194305, 8390831, 16777233, 33558531, 67109125, 134225995, 268435457, 536887863, 1073741825, 2147516555, 4294968325, 8590000131 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Dirichlet convolution of b_n=1 with c_n=2^(n-1).
Equals row sums of triangle A143425, & inverse Möbius transform (A051731) of [1, 2, 4, 8, ...]. - Gary W. Adamson, Aug 14 2008
Number of constant multiset partitions of normal multisets of size n, where a multiset is normal if it spans an initial interval of positive integers. - Gus Wiseman, Sep 16 2018
LINKS
FORMULA
G.f.: Sum_{n>0} x^n/(1-2*x^n). - Vladeta Jovovic, Nov 14 2002
a(n) = 1/2 * A055895(n). - Joerg Arndt, Aug 14 2012
G.f.: Sum_{n>=1} 2^(n-1) * x^n / (1 - x^n). - Paul D. Hanna, Aug 21 2014
G.f.: Sum_{n>=1} x^n * Sum_{d|n} 1/(1 - x^d)^(n/d). - Paul D. Hanna, Aug 21 2014
a(n) ~ 2^(n-1). - Vaclav Kotesovec, Sep 09 2014
a(n) = Sum_{k in row n of A215366} A008480(k) * A000005(A289508(k)). - Gus Wiseman, Sep 16 2018
a(n) = Sum_{c is a composition of n} A000005(gcd(c)). - Gus Wiseman, Sep 16 2018
EXAMPLE
From Gus Wiseman, Sep 16 2018: (Start)
The a(4) = 11 constant multiset partitions:
(1)(1)(1)(1)
(11)(11)
(12)(12)
(1111)
(1222)
(1122)
(1112)
(1233)
(1223)
(1123)
(1234)
(End)
MAPLE
seq(add(2^(k-1), k=numtheory:-divisors(n)), n = 1 .. 100); # Robert Israel, Aug 22 2014
MATHEMATICA
Rest[CoefficientList[Series[Sum[x^k/(1-2*x^k), {k, 1, 30}], {x, 0, 30}], x]] (* Vaclav Kotesovec, Sep 08 2014 *)
PROG
(PARI) A034729(n) = sumdiv(n, k, 2^(k-1)) \\ Michael B. Porter, Mar 11 2010
(PARI) {a(n)=polcoeff(sum(m=1, n, 2^(m-1)*x^m/(1-x^m +x*O(x^n))), n)}
for(n=1, 40, print1(a(n), ", ")) \\ Paul D. Hanna, Aug 21 2014
(PARI) {a(n)=local(A=x+x^2); A=sum(m=1, n, x^m*sumdiv(m, d, 1/(1 - x^(m/d) +x*O(x^n))^d) ); polcoeff(A, n)}
for(n=1, 40, print1(a(n), ", ")) \\ Paul D. Hanna, Aug 21 2014
(Python)
from sympy import divisors
def A034729(n): return sum(1<<(d-1) for d in divisors(n, generator=True)) # Chai Wah Wu, Jul 15 2022
CROSSREFS
Sequence in context: A155989 A125557 A007455 * A115786 A252089 A128550
KEYWORD
nonn
AUTHOR
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 18 15:24 EDT 2024. Contains 372664 sequences. (Running on oeis4.)