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A168426 Square array of denominators of a truncated array of Bernoulli twin numbers (A168516), read by antidiagonals. 5
3, 6, 6, 30, 15, 30, 30, 15, 15, 30, 42, 105, 105, 105, 42, 42, 21, 105, 105, 21, 42, 30, 105, 105, 105, 105, 105, 30, 30, 15, 105, 105, 105, 105, 15, 30, 66, 165, 165, 1155, 231, 1155, 165, 165, 66, 66, 33, 165, 165, 231, 231, 165, 165, 33, 66, 2730, 15015, 15015, 15015, 15015, 15015, 15015, 15015 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Entries are multiples of 3.

The sequence of fractions A051716()/A051717() is a sequence of first differences of A164555()/A027642().

It can be observed (see the difference array in A190339) that A168516/A168426 is a sequence of autosequences of the second kind. - Paul Curtz, Dec 21 2016

LINKS

Table of n, a(n) for n=0..62.

MATHEMATICA

max = 11; c[0] = 1; c[n_?EvenQ] := BernoulliB[n] + BernoulliB[n-1]; c[n_?OddQ] := -BernoulliB[n] - BernoulliB[n-1]; cc = Table[c[n], {n, 0, max+1}]; diff = Drop[#, 2]& /@ Table[ Differences[cc, n], {n, 0, max-1}]; Flatten[ Table[ diff[[n-k+1, k]], {n, 1, max}, {k, 1, n}]] // Denominator (* Jean-Fran├žois Alcover, Aug 09 2012 *)

CROSSREFS

Cf. A085738, A085737, A168516, A190339, A240581/A239315.

Sequence in context: A223048 A319446 A181372 * A065931 A137497 A032338

Adjacent sequences:  A168423 A168424 A168425 * A168427 A168428 A168429

KEYWORD

nonn,tabl,frac

AUTHOR

Paul Curtz, Nov 25 2009

EXTENSIONS

More terms from R. J. Mathar, Jul 10 2011

STATUS

approved

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Last modified July 8 01:25 EDT 2020. Contains 335502 sequences. (Running on oeis4.)