A238691 a(n) = A190339(n)/A224911(n).

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

Author

Paul Curtz, Mar 03 2014

Keywords

• nonn

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).

Examples

			a(0)=2/2=1, a(1)=6/3=2, a(2)=15/5=3, a(3)=a(4)=105/7=15, ... .
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200

Crossrefs

Cf. A060308.

Programs

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]]

Extensions

a(16)-a(25) from Jean-François Alcover, Mar 03 2014