login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A206770 Smallest number k such that sigma(k-2*n)=sigma(k)-2*n. 1
5, 7, 11, 11, 13, 17, 17, 19, 23, 23, 29, 29, 21, 31, 37, 37, 37, 41, 28, 33, 47, 47, 53, 53, 53, 59, 59, 44, 61, 67, 67, 67, 71, 57, 73, 79, 79, 79, 83, 83, 69, 89, 74, 101, 68, 97, 97, 85, 101, 103, 107, 107, 109, 113, 93, 131, 127, 127, 131, 127, 127, 127 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Note all k>=1 are considered, even if k-2n<0. If the search space is k>=2n, variants of A020484 and A060264 appear. - R. J. Mathar, Jan 12 2013

LINKS

Table of n, a(n) for n=1..62.

EXAMPLE

a(15)=37 because 37 is the minimum number for which sigma(37-2*15)=sigma(7)=8 and sigma(37)-2*15=38-30=8.

MAPLE

A206770:=proc(q)

local k, n;

for n from 1 to q do

for k from 1 to q do

  if sigma(k-2*n)=sigma(k)-2*n then print(k); break; fi;

od; od; end:

A206770(1000000000);

A206770 := proc(n)

    local k ;

    for k from 1 do

        if numtheory[sigma](k-2*n) = numtheory[sigma](k)-2*n then

            return k;

        end if;

    end do:

end proc: # R. J. Mathar, Jan 12 2013

CROSSREFS

Cf. A054906

Sequence in context: A104200 A249916 A115044 * A107257 A275515 A098806

Adjacent sequences:  A206767 A206768 A206769 * A206771 A206772 A206773

KEYWORD

nonn

AUTHOR

Paolo P. Lava, Jan 10 2013

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 February 23 09:04 EST 2019. Contains 320420 sequences. (Running on oeis4.)