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5x - 1 sequence starting at 19 (a(n+1) = a(n)/2 if a(n) is even, or 5*a(n)-1 if a(n) is odd).
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%I #14 Sep 14 2024 09:32:16

%S 19,94,47,234,117,584,292,146,73,364,182,91,454,227,1134,567,2834,

%T 1417,7084,3542,1771,8854,4427,22134,11067,55334,27667,138334,69167,

%U 345834,172917,864584,432292,216146,108073,540364,270182,135091,675454,337727

%N 5x - 1 sequence starting at 19 (a(n+1) = a(n)/2 if a(n) is even, or 5*a(n)-1 if a(n) is odd).

%C Reaches 4, 2, 1, 4, 2, 1, ... in 437 steps. - _T. D. Noe_, Mar 01 2008

%H T. D. Noe, <a href="/A037238/b037238.txt">Table of n, a(n) for n=1..437</a>

%t NestList[If[EvenQ[#], #/2, 5# - 1] &, 19, 100] (* _Alonso del Arte_, Nov 19 2020 *)

%o (Scala) def fiveX(n: Int): Int = n % 2 match {

%o case 0 => n / 2

%o case _ => 5 * n - 1

%o }

%o val A037238 = LazyList.iterate(19)(fiveX)

%o A037238.take(100).toList // _Alonso del Arte_, Nov 19 2020

%Y Cf. A090691.

%K nonn,easy

%O 1,1

%A Dan Goldwater (dan(AT)craftech.com)

%E More terms from _Erich Friedman_.

%E Definition clarified by _N. J. A. Sloane_, Sep 14 2024