login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A050460 a(n) = Sum_{ d divides n, n/d=1 mod 4} d. 6
1, 2, 3, 4, 6, 6, 7, 8, 10, 12, 11, 12, 14, 14, 18, 16, 18, 20, 19, 24, 22, 22, 23, 24, 31, 28, 30, 28, 30, 36, 31, 32, 34, 36, 42, 40, 38, 38, 42, 48, 42, 44, 43, 44, 60, 46, 47, 48, 50, 62, 54, 56, 54, 60, 66, 56, 58, 60, 59, 72, 62, 62, 73, 64, 84, 68 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Not multiplicative: a(3)*a(7) <> a(21), for example.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: Sum_{n>0} n*x^n/(1-x^(4*n)). - Vladeta Jovovic, Nov 14 2002

MAPLE

A050460 := proc(n)

        a := 0 ;

        for d in numtheory[divisors](n) do

                if (n/d) mod 4 = 1 then

                        a := a+d ;

                end if;

        end do:

        a;

end proc:

seq(A050460(n), n=1..40) ; # R. J. Mathar, Dec 20 2011

MATHEMATICA

a[n_] := DivisorSum[n, Boole[Mod[n/#, 4] == 1]*#&]; Array[a, 70] (* Jean-Fran├žois Alcover, Dec 01 2015 *)

PROG

(PARI) a(n)=sumdiv(n, d, if(n/d%4==1, d)) \\ Charles R Greathouse IV, Dec 04 2013

CROSSREFS

Cf. A050449, A001826.

Sequence in context: A060019 A093451 A106006 * A246594 A175808 A334666

Adjacent sequences:  A050457 A050458 A050459 * A050461 A050462 A050463

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 23 1999

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 26 09:03 EDT 2020. Contains 338027 sequences. (Running on oeis4.)