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A046212 First numerator and then denominator of central elements of Leibniz's Harmonic Triangle. 20
1, 1, 1, 6, 1, 30, 1, 140, 1, 630, 1, 2772, 1, 12012, 1, 51480, 1, 218790, 1, 923780, 1, 3879876, 1, 16224936, 1, 67603900, 1, 280816200, 1, 1163381400, 1, 4808643120, 1, 19835652870, 1, 81676217700, 1, 335780006100, 1, 1378465288200, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 83, Problem 25.

LINKS

Table of n, a(n) for n=1..41.

FORMULA

a(2n+1)=A056040(2n+1)=A100071(2n+1). - M. F. Hasler, Jan 25 2012

CROSSREFS

Cf. A003506.

Cf. A002457.

Sequence in context: A193633 A176289 A118933 * A120105 A120101 A178726

Adjacent sequences:  A046209 A046210 A046211 * A046213 A046214 A046215

KEYWORD

nonn,easy

AUTHOR

Mohammad K. Azarian

EXTENSIONS

More terms from James A. Sellers, Dec 13 1999

STATUS

approved

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Last modified November 20 15:12 EST 2018. Contains 317402 sequences. (Running on oeis4.)