login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A348093 Numbers k >= 1 such that there is no pair (x,y) such that x - d(x) = k and y + d(y) = k, where d = A000005 = number of divisors. 0
8, 20, 36, 40, 67, 68, 79, 88, 100, 116, 117, 131, 132, 134, 140, 156, 164, 167, 180, 185, 196, 204, 228, 244, 252, 268, 276, 284, 300, 308, 312, 321, 324, 341, 348, 370, 372, 379, 388, 401, 405, 408, 420, 425, 436, 439, 453, 460, 476, 479 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..50.

FORMULA

A060990(k) + A036431(k) = 0

EXAMPLE

k = 8 is a term: there are no x,y such that x - d(x) = 8, y + d(y) = 8.

PROG

(PARI) okp(k) = sum(i=1, k, i+numdiv(i) == k) == 0;

okm(k) = sum(i=1, 2*k+2, i-numdiv(i) == k) == 0;

isok(k) = okp(k) && okm(k); \\ Michel Marcus, Oct 01 2021

CROSSREFS

Cf. A000005, A036431, A049820, A060990, A062249.

Intersection of A036434 and A045765.

Sequence in context: A246309 A038522 A267435 * A186293 A158865 A139570

Adjacent sequences: A348090 A348091 A348092 * A348094 A348095 A348096

KEYWORD

nonn

AUTHOR

Ctibor O. Zizka, Sep 29 2021

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 November 26 21:15 EST 2022. Contains 358362 sequences. (Running on oeis4.)