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A051230 Bernoulli number B_{n} has denominator 66. 38
10, 50, 170, 370, 470, 590, 610, 670, 710, 730, 790, 850, 1010, 1070, 1270, 1370, 1390, 1490, 1630, 1670, 1850, 1970, 1990, 2230, 2270, 2290, 2570, 2630, 2690, 2770, 2830, 2890, 2950, 3050, 3070, 3110, 3130, 3170, 3310, 3350, 3470, 3530 (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.

Numerator(B_{n}) mod denominator(B_{n}) = 5. - Paolo P. Lava, Mar 30 2015

REFERENCES

B. C. Berndt, Ramanujan's Notebooks Part IV, Springer-Verlag, see p. 75.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for sequences related to Bernoulli numbers.

MATHEMATICA

denoBn[n_?EvenQ] := Times @@ Select[Prime /@ Range[PrimePi[n] + 1], Divisible[n, # - 1] & ]; Select[ Range[10, 4000, 10], denoBn[#] == 66 &] (* Jean-Fran├žois Alcover, Jun 27 2012, after comments *)

Flatten[Position[BernoulliB[Range[4000]], _?(Denominator[#]==66&)]] (* Harvey P. Dale, Nov 17 2014 *)

PROG

(PARI) /* define indicator function */ a(n)=local(s); s=0; fordiv(n, d, s+=isprime(d+1)&(d>2)&(d!=10)); !s /* get sequence */ an=vector(45, n, 0); m=0; forstep(n=10, 4000, 10, if(a(n), an[ m++ ]=n)); for(n=1, 42, print1(an[ n ]", "))

CROSSREFS

Cf. A045979, A051222, A051225-A051229. Equals 2*A051229.

Sequence in context: A153780 A196507 A008531 * A008413 A006542 A237655

Adjacent sequences:  A051227 A051228 A051229 * A051231 A051232 A051233

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Michael Somos

STATUS

approved

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Last modified March 22 04:32 EDT 2019. Contains 321406 sequences. (Running on oeis4.)