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A215085 a(n) = (A214089(n)^2 - 1) divided by four times the product of the first n primes. 3
1, 1, 1, 1, 19, 17, 1, 2567, 3350, 128928, 3706896, 1290179, 100170428, 39080794, 61998759572, 7833495265, 45119290746, 581075656330, 8672770990, 15792702394898740, 594681417768520250, 25509154378676494, 1642780344643617537867, 480931910076867717575 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

When floor(A214089(n) / 2) = A118478(n), a(n) = A215021(n).

LINKS

J. Stauduhar, Table of n, a(n) for n = 1..30

FORMULA

a(n) = (A214089(n)^2 - 1) / (4 * A002110(n)).

EXAMPLE

a214089(14) = 1430083494841, n#_14 = 13082761331670030, and (1430083494841^2 - 1) / (4 * 13082761331670030) = 39080794, so a(14) = 39080794.

MAPLE

A215085 := proc(n)

        (A214089(n)^2-1)/4/A002110(n) ;

end proc: # R. J. Mathar, Aug 21 2012

CROSSREFS

Sequence in context: A269231 A135734 A215021 * A241525 A321332 A109410

Adjacent sequences:  A215082 A215083 A215084 * A215086 A215087 A215088

KEYWORD

nonn

AUTHOR

J. Stauduhar, Aug 02 2012

STATUS

approved

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Last modified June 19 08:58 EDT 2021. Contains 345126 sequences. (Running on oeis4.)