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A238691
a(n) = A190339(n)/A224911(n).
2
1, 2, 3, 15, 15, 21, 1155, 165, 2145, 51051, 255255, 440895, 440895, 969, 111435, 248834355, 248834355, 2927463, 5898837945, 44352165, 1641030105, 8563193457, 42815967285, 80047243185, 1360803134145, 32898537309, 7731156267615, 1028243783592795, 1028243783592795, 375840831244263
OFFSET
0,2
COMMENTS
Are non-repeated terms of A224911(n) (2,3,5,11,17,...) A124588(n+1)?
Are repeated terms of A224911(n) (7,13,19,23,31,37,...) A049591(n+1)? At that sequence, Benoit Cloitre mentions a link to the Bernoulli numbers.
Greatest primes dividing a(n): 1, 2, 3, 5, 5, 7, 11, 11, 13, 17, 17, 19, 19, 19, 23, 29, 29, 29, ... = b(n). It appears that b(n) is A224911(n) with A008578(n), ancient primes, instead of A000040(n).
Hence c(n) = 2, 6, 15, 35, ... = 2, followed by A006094(n+1).
LINKS
EXAMPLE
a(0)=2/2=1, a(1)=6/3=2, a(2)=15/5=3, a(3)=a(4)=105/7=15, ... .
MATHEMATICA
nmax = 40; b[n_] := BernoulliB[n]; b[1] = 1/2; bb = Table[b[n], {n, 0, 2*nmax-1}]; diff = Table[Differences[bb, n], {n, 1, nmax}]; (#/FactorInteger[#][[-1, 1]])& /@ Denominator[Diagonal[diff]]
CROSSREFS
Cf. A060308.
Sequence in context: A101047 A251618 A309765 * A241721 A066491 A282383
KEYWORD
nonn
AUTHOR
Paul Curtz, Mar 03 2014
EXTENSIONS
a(16)-a(25) from Jean-François Alcover, Mar 03 2014
STATUS
approved