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A303658 Decimal expansion of the alternating sum of the reciprocals of the triangular numbers. 1
7, 7, 2, 5, 8, 8, 7, 2, 2, 2, 3, 9, 7, 8, 1, 2, 3, 7, 6, 6, 8, 9, 2, 8, 4, 8, 5, 8, 3, 2, 7, 0, 6, 2, 7, 2, 3, 0, 2, 0, 0, 0, 5, 3, 7, 4, 4, 1, 0, 2, 1, 0, 1, 6, 4, 8, 2, 7, 2, 0, 0, 3, 7, 9, 7, 3, 5, 7, 4, 4, 8, 7, 8, 7, 8, 7, 7, 8, 8, 6, 2, 4, 2, 3, 4, 5, 3 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..86.

FORMULA

Equals log(16/e^2) = log(16) - 2.

EXAMPLE

1/1 - 1/3 + 1/6 - 1/10 + 1/15 - 1/21 + ... = 0.77258872223978123766892848583270627230200053744102...

PROG

(PARI) sumalt(n=1, (-1)^(n+1)*2/(n*(n+1))) \\ Michel Marcus, Apr 28 2018

(PARI) log(16)-2 \\ Altug Alkan, May 07 2018

CROSSREFS

Cf. A000217 (triangular numbers). Apart from leading digit the same as A016639 (log(16)).

Sequence in context: A002161 A083871 A255272 * A169812 A195907 A126584

Adjacent sequences:  A303655 A303656 A303657 * A303659 A303660 A303661

KEYWORD

nonn,cons

AUTHOR

Jon E. Schoenfield, Apr 28 2018

STATUS

approved

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Last modified December 15 00:30 EST 2019. Contains 329988 sequences. (Running on oeis4.)