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A105573 Numbers m such that m-4 and m+4 have 4 prime factors. 3
20, 136, 200, 224, 344, 346, 368, 376, 480, 488, 554, 568, 576, 640, 736, 744, 808, 816, 854, 856, 864, 872, 880, 944, 992, 1064, 1152, 1160, 1200, 1208, 1214, 1216, 1280, 1288, 1312, 1360, 1426, 1568, 1576, 1606, 1621, 1648, 1656, 1664, 1784, 1808, 1858 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A001222(a(n)-4) = A001222(a(n)+4) = 4.

Prime factors counted with multiplicity. - Harvey P. Dale, Feb 06 2020

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

1214 - 4 = 1210 = 2 * 5 * 11 * 11 and 1214 + 4 = 1218 = 2 * 3 * 7 * 29 so 1214 is in the sequence. - Jon E. Schoenfield, Jan 19 2015

MATHEMATICA

q=4; lst={}; Do[If[Plus@@Last/@FactorInteger[n-q]==q&&Plus@@Last/@FactorInteger[n+q]==q, AppendTo[lst, n]], {n, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Feb 01 2009 *)

Mean/@SequencePosition[PrimeOmega[Range[2000]], {4, _, _, _, _, _, _, _, 4}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Feb 06 2020 *)

CROSSREFS

Cf. A014574, A105571, A105572.

Sequence in context: A188145 A168178 A085284 * A144965 A262140 A140301

Adjacent sequences:  A105570 A105571 A105572 * A105574 A105575 A105576

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 14 2005

STATUS

approved

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Last modified July 2 08:02 EDT 2020. Contains 335398 sequences. (Running on oeis4.)