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!)
A051228 Numbers m such that the Bernoulli number B_m has denominator 42. 32
6, 114, 186, 258, 354, 402, 426, 474, 582, 654, 762, 834, 894, 942, 978, 1002, 1158, 1182, 1194, 1266, 1338, 1362, 1374, 1614, 1842, 1902, 2022, 2094, 2118, 2166, 2274, 2298, 2334, 2406, 2454, 2526, 2598, 2634, 2694, 2742, 2778, 2874, 2922, 2994, 3126 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
From the von Staudt-Clausen theorem, denominator(B_{2*m}) = product of primes p such that (p-1)|2*m.
REFERENCES
B. C. Berndt, Ramanujan's Notebooks Part IV, Springer-Verlag, see p. 75.
LINKS
FORMULA
a(n) = 2*A051227(n). - Petros Hadjicostas, Jun 06 2020
MATHEMATICA
2*Select[Range[2000], Denominator[BernoulliB[2#]] == 42 &](* Jean-François Alcover, Nov 25 2011 *)
Position[BernoulliB[Range[3200]], _?(Denominator[#]==42&)]//Flatten (* Harvey P. Dale, Jul 02 2018 *)
PROG
(Perl) @p=(2, 3, 5, 7); @c=(4); $p=7; for($n=6; $n<=3126; $n+=6){while($p<$n+1){$p+=2; next if grep$p%$_==0, @p; push@p, $p; push@c, $p-1; }print"$n, "if!grep$n%$_==0, @c; }print"\n"
(PARI) is(n)=denominator(bernfrac(n))==42 \\ Charles R Greathouse IV, Feb 07 2017
CROSSREFS
Sequence in context: A291917 A066931 A324669 * A194132 A194476 A059116
KEYWORD
nonn,nice,easy
AUTHOR
EXTENSIONS
More terms and Perl program from Hugo van der Sanden
Name edited by Petros Hadjicostas, Jun 06 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 16:28 EDT 2024. Contains 371254 sequences. (Running on oeis4.)