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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A154296 Primes of the form (1+2+3+...+m)/15 = A000217(m)/15, for some m. 9
3, 7, 29, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Original definition : Primes of the form 1/x+2/x+3/x+4/x+5/x+6/x+7/x+..., x=15.

The corresponding m-values are m=9, 14, 29, 30. It is clear that for m>30, T(m)/15 = m(m+1)/30 cannot be a prime. - M. F. Hasler, Dec 31 2012

All of the sequences A154296, ..., A154304 could or should be grouped together in a single ("fuzzy"?) table. It would be more interesting to have the function f(n) which gives the *number* of primes of the form T(k)/n. - M. F. Hasler, Jan 06 2013

LINKS

Table of n, a(n) for n=1..4.

MATHEMATICA

lst={}; s=0; Do[s+=n/15; If[Floor[s]==s, If[PrimeQ[s], AppendTo[lst, s]]], {n, 0, 9!}]; lst

Select[(Accumulate[Range[200]])/15, PrimeQ] (* Harvey P. Dale, Oct 30 2011 *)

PROG

(PARI) select(x->denominator(x)==1 & isprime(x), vector(30, m, m^2+m)/30)  \\ - M. F. Hasler, Dec 31 2012

CROSSREFS

Cf. A057570, A154293, A154297, A154298, A154299, A154300, A154301, A154302, A154303, A154304.

Sequence in context: A018989 A325258 A073126 * A038900 A068485 A019352

Adjacent sequences:  A154293 A154294 A154295 * A154297 A154298 A154299

KEYWORD

nonn,fini,full,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jan 06 2009

EXTENSIONS

Edited by M. F. Hasler, Dec 31 2012

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 19 03:54 EDT 2019. Contains 328211 sequences. (Running on oeis4.)