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A167394 Largest single or isolated prime < n-th single or isolated composite. 1
2, 2, 2, 2, 23, 37, 53, 67, 97, 97, 131, 131, 173, 173, 173, 223, 233, 263, 277, 307, 337, 409, 409, 457, 509, 563, 593, 613, 631, 653, 797, 797, 797, 853, 877, 1013, 1013, 1039, 1039, 1087, 1129, 1223, 1259, 1283, 1297, 1307, 1423, 1447, 1471, 1471, 1601, 1613 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..52.

MAPLE

isA007510 := proc(n) isprime(n) and not isprime(n+2) and not isprime(n-2) ; simplify(%) ; end proc:

A167394 := proc(n) local a; for a from A014574(n)-1 by -1 do if isA007510(a) then return a; end if; end do: end proc:

seq(A167394(n), n=1..120) ; # R. J. Mathar, May 30 2010

CROSSREFS

Cf. A007510, A014574.

Sequence in context: A067096 A259704 A249779 * A029627 A075182 A292023

Adjacent sequences:  A167391 A167392 A167393 * A167395 A167396 A167397

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Nov 02 2009

EXTENSIONS

Corrected (47 replaced with 53, 211 replaced with 223, etc.) by R. J. Mathar, May 30 2010

STATUS

approved

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Last modified December 1 16:23 EST 2021. Contains 349430 sequences. (Running on oeis4.)