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 A051230 Bernoulli number B_{n} has denominator 66. 10
 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. 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 MATHEMATICA denoBn[n_?EvenQ] := Times @@ Select[Prime /@ Range[PrimePi[n] + 1], Divisible[n, # - 1] & ]; Select[ Range[10, 4000, 10], denoBn[#] == 66 &] (* Jean-François Alcover, Jun 27 2012, after comments *) 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 A086462 Adjacent sequences:  A051227 A051228 A051229 * A051231 A051232 A051233 KEYWORD nonn,nice,easy AUTHOR EXTENSIONS More terms from Michael Somos. STATUS approved

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Last modified May 22 05:06 EDT 2013. Contains 225511 sequences.