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!)
A306745 Even bisection of A318256. 1
1, 2, 6, 6, 10, 6, 210, 2, 30, 210, 110, 30, 546, 14, 30, 462, 1190, 6, 51870, 70, 2310, 2310, 322, 210, 6630, 286, 330, 798, 290, 30, 930930, 1430, 1122, 82110, 70, 330, 21111090, 38038, 390, 210, 536690, 39270, 7489482, 10010, 62790, 4470510, 687610, 462 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The ratio sequence of a(n)/A006955(n) begins: 1,1,1,1,1,1,1,1,1,5,1,5,1,7,1,1,7,1,1,35, ...

This divisibility by A006955 was confirmed by Peter Luschny in the SeqFan mailing list.

LINKS

Jean-François Alcover, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = (denominator of B(2n,x)) / (the squarefree kernel of 2n+1), where B(2n,x) is the 2n-th Bernoulli polynomial.

MATHEMATICA

sfk[n_] := Times @@ FactorInteger[n][[All, 1]];

a[n_] := (BernoulliB[2 n, x] // Together // Denominator)/sfk[2 n + 1];

Table[a[n], {n, 0, 60}]

CROSSREFS

Cf. A006955, A318256.

Sequence in context: A021978 A141377 A006955 * A196053 A063210 A114718

Adjacent sequences:  A306742 A306743 A306744 * A306746 A306747 A306748

KEYWORD

nonn

AUTHOR

Jean-François Alcover and Paul Curtz, Mar 07 2019

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 July 25 19:34 EDT 2021. Contains 346291 sequences. (Running on oeis4.)