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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
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OFFSET
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0,2
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COMMENTS
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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).
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LINKS
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EXAMPLE
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a(0)=2/2=1, a(1)=6/3=2, a(2)=15/5=3, a(3)=a(4)=105/7=15, ... .
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MATHEMATICA
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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]]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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