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!)
A334084 Integers m such that only 2 binomial coefficients C(m,k), with 0<=k<=m, are practical numbers. 2
1, 3, 5, 7, 15, 31, 63, 127, 255, 511, 1023 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Integers m such that A334082(m) = m-1.

Integers of the form 2^k-1 with k>0 are terms, but this condition is not necessary since 5 is a term.

LINKS

Table of n, a(n) for n=1..11.

PROG

(PARI) isok(n) = sum(k=0, n, !is_A005153(binomial(n, k))) == n-1;

CROSSREFS

Cf. A005153 (practical numbers), A007318 (binomial coefficients).

Cf. A334082, A334083.

Sequence in context: A261646 A303027 A217615 * A050553 A005540 A155802

Adjacent sequences:  A334081 A334082 A334083 * A334085 A334086 A334087

KEYWORD

nonn,more

AUTHOR

Michel Marcus, Apr 14 2020

EXTENSIONS

a(11) from Jinyuan Wang, Apr 14 2020

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 April 20 23:46 EDT 2021. Contains 343143 sequences. (Running on oeis4.)