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A252995 Numbers n such that the n-th odd composite number is 3n. 0
335, 337, 339, 343, 349, 353, 359, 365, 367, 369, 371, 373, 375, 377 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The sequence is finite, since lim A071904(n)/n = 2.

LINKS

Table of n, a(n) for n=1..14.

FORMULA

Define b(k) = 6k + 3 for k > 0. Delete all terms except those such that (b(k) - 1)/2 - pi(k) + 1 = b(k)/3. Then a(k) = b(k)/3. - Alonso del Arte, Dec 25 2014

EXAMPLE

a(1) = 335, since, for n <= 334, A071904(n) > 3*n, while A071904(335) = 3*335.

a(14) = 377 is the last term, since, A071904(377) = 3*377, while A071904(n) < 3*n, for n >= 378.

MATHEMATICA

Select[Range[9, 1197, 6], (# - 1)/2 - PrimePi[#] + 1 == #/3 &]/3 (* Alonso del Arte, Dec 25 2014 *)

CROSSREFS

Cf. A071904.

Sequence in context: A278098 A303209 A216138 * A119760 A046015 A184076

Adjacent sequences:  A252992 A252993 A252994 * A252996 A252997 A252998

KEYWORD

nonn,fini,full

AUTHOR

Vladimir Shevelev, Dec 25 2014

STATUS

approved

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Last modified January 21 03:58 EST 2022. Contains 350473 sequences. (Running on oeis4.)