A237425 - OEIS

A237425

Denominators of A164555(n)/A027642(n) + A198631(n)/A006519(n+1).

1, 1, 6, 4, 30, 2, 42, 8, 30, 2, 66, 4, 2730, 2, 6, 16, 510, 2, 798, 4, 330, 2, 138, 8, 2730, 2, 6, 4, 870, 2, 14322, 32, 510, 2, 6, 4, 1919190, 2, 6, 8, 13530, 2, 1806, 4, 690, 2, 282, 16, 46410, 2, 66, 4, 1590, 2, 798, 8

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OFFSET

0,3

COMMENTS

An autosequence is a sequence which has its inverse binomial transform equal to the signed sequence. There are two possibilities. For the first kind, the main diagonal is 0's=A000004, the first two following diagonals being the same (generally not A000004). Integers example: A000045(n).

For the second kind, the main diagonal is the double of the following diagonal. Example: the companion to A000045(n) is A000032(n)=2, 1, 3, ... .

A000032(n)/2 is also a possibility. Here a(n) is the denominator of the sum of two autosequences of second kind involving (fractional) Euler and Bernoulli numbers. The corresponding fractional sequence is also an autosequence of the second kind: 2, 1, 1/6, -1/4, -1/30, 1/2, 1/42, -17/8, -1/30, 31/2, 5/66, -691/4, -691/2730,... . It could be divided by 2.

LINKS

Table of n, a(n) for n=0..55.

FORMULA

a(2n) = A002445(n). a(2n+2) = A171977(n+2).

MATHEMATICA

a[n_] := BernoulliB[n] + EulerE[n, 1]/2^IntegerExponent[n, 2]; a[0] = 2; a[1] = 1; Table[a[n] // Denominator, {n, 0, 55}] (* Jean-François Alcover, Feb 11 2014 *)

CROSSREFS

Cf. 1/n in A003506, A194767, A218289, A168516/A168426, A224270/A046161.

Sequence in context: A133837 A211945 A121682 * A191567 A274707 A372524

Adjacent sequences: A237422 A237423 A237424 * A237426 A237427 A237428

KEYWORD

nonn

AUTHOR

Paul Curtz, Feb 07 2014

STATUS

approved