A071260 - OEIS

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A071260

Integer part of the geometric mean of the n-th prime prime(n) and the n-th composite number C(n).

2, 4, 6, 7, 10, 12, 15, 16, 19, 22, 24, 27, 30, 32, 34, 37, 39, 41, 44, 47, 49, 51, 53, 56, 60, 62, 64, 67, 69, 71, 76, 79, 81, 83, 87, 88, 92, 94, 96, 99, 101, 104, 108, 110, 112, 113, 118, 123, 125, 126, 129, 132, 134, 138, 140, 143, 146, 148, 150, 153, 155, 158

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

FORMULA

Floor [ {prime(n)* C(n)}^(1/2)]

EXAMPLE

a(7) =floor {prime(7)*C(7)}^(1/2) = (17*14)^1/2 = 15.

MATHEMATICA

Module[{nn=100, prs, cmps, len}, prs=Prime[Range[nn]]; cmps=Select[ Range[ nn+Length[prs]], CompositeQ]; len=Min[Length[cmps], Length[prs]]; IntegerPart[ GeometricMean[#]]&/@Thread[{Take[prs, len], Take[ cmps, len]}]] (* Harvey P. Dale, Aug 12 2016 *)

CROSSREFS

Cf. A071259.

Sequence in context: A189030 A198033 A375598 * A026407 A003035 A094453

Adjacent sequences: A071257 A071258 A071259 * A071261 A071262 A071263

KEYWORD

nonn

AUTHOR

Amarnath Murthy, May 30 2002

EXTENSIONS

More terms from Hans Havermann, Sep 23 2002

STATUS

approved