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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A027762 Denominator of Sum_{p prime, p-1 divides 2*n} 1/p. 8
6, 30, 42, 30, 66, 2730, 6, 510, 798, 330, 138, 2730, 6, 870, 14322, 510, 6, 1919190, 6, 13530, 1806, 690, 282, 46410, 66, 1590, 798, 870, 354, 56786730, 6, 510, 64722, 30, 4686, 140100870, 6, 30, 3318, 230010, 498, 3404310, 6, 61410, 272118, 1410, 6, 4501770 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
From the von Staudt-Clausen theorem, denominator(B_2n) = product of primes p such that (p-1)|2n.
Same as A002445.
REFERENCES
G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, Th. 118.
H. Rademacher, Topics in Analytic Number Theory, Springer, 1973, Chap. 1.
LINKS
R. Mestrovic, On a Congruence Modulo n^3 Involving Two Consecutive Sums of Powers, Journal of Integer Sequences, Vol. 17 (2014), 14.8.4.
FORMULA
a(n) = A002445(n). [Joerg Arndt, May 06 2012]
a(n) = A027760(2*n). - Ridouane Oudra, Feb 22 2022
PROG
(PARI)
a(n)=
{
my(s=0);
forprime (p=2, 2*n+1, if( (2*n)%(p-1)==0, s+=1/p ) );
return( denominator(s) );
}
/* Joerg Arndt, May 06 2012 */
CROSSREFS
Cf. A027760.
Sequence in context: A334900 A136375 A138706 * A002445 A151711 A130512
KEYWORD
nonn,frac
AUTHOR
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 March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)