This site is supported by donations to The OEIS Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 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] 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. A027761, A006954. Sequence in context: A067879 A136375 A138706 * A002445 A151711 A130512 Adjacent sequences:  A027759 A027760 A027761 * A027763 A027764 A027765 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 19 06:08 EST 2019. Contains 319304 sequences. (Running on oeis4.)