

A228047


Decimal expansion of sum of reciprocals, row 5 of the natural number array, A185787.


6



4, 2, 3, 5, 3, 9, 0, 9, 9, 6, 0, 8, 7, 0, 0, 1, 9, 6, 8, 3, 7, 6, 0, 7, 6, 8, 9, 9, 7, 4, 4, 2, 8, 9, 3, 7, 5, 4, 4, 3, 2, 2, 8, 8, 1, 8, 9, 4, 1, 7, 1, 1, 1, 0, 2, 1, 7, 5, 6, 0, 8, 4, 2, 8, 1, 3, 0, 9, 3, 4, 7, 8, 2, 4, 5, 8, 2, 6, 7, 1, 1, 7, 8, 2, 5, 9
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OFFSET

0,1


COMMENTS

Let s(n) be the sum of reciprocals of the numbers in row n of the array T at A185787 given by T(n,k) = n + (n+k2)(n+k1)/2, and let r = (2*pi/sqrt(7))*tanh(pi*sqrt(7)/2), as at A226985. Then s(1) = r, and s(2) to s(5) are given by A228044 to A228047.
Let c(n) be the sum of reciprocals of the numbers in column n of T. Then c(1) = 2; c(2) = 11/9, c(4) = 29/50, and c(3) is given by A228049. Let d(n) be the sum of reciprocals of the numbers in the main diagonal, (T(n,n)); then d(2) = (1/12)*(pi)^2; d(3) = 1/2, and d(1) is given by A228048.


LINKS

Table of n, a(n) for n=0..85.


EXAMPLE

1/15 + 1/20 + 1/26 + ... = (1/17160)(9997 + 1760r*tanh(r)), where r = (pi/2)*sqrt(39)
1/15 + 1/20 + 1/26 + ... = 0.42353909960870019683760768997442893...


MATHEMATICA

$MaxExtraPrecision = Infinity; t[n_, k_] := t[n, k] = n + (n + k  2) (n + k  1)/2; u = N[Sum[1/t[5, k], {k, 1, Infinity}], 130]; RealDigits[u, 10]


CROSSREFS

Cf. A185787, A000027, A228044, A226985.
Sequence in context: A274791 A200024 A247206 * A188543 A182272 A182273
Adjacent sequences: A228044 A228045 A228046 * A228048 A228049 A228050


KEYWORD

nonn,cons,easy


AUTHOR

Clark Kimberling, Aug 06 2013


STATUS

approved



