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A022803 Numbers that reach ...,7,8,4,2,1 under the mapping: if n is even divide by 2 else add 1. 3
13, 14, 25, 26, 27, 28, 49, 50, 51, 52, 53, 54, 55, 56, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

7 itself does not qualify, by decree. - N. J. A. Sloane, Sep 02 2017

LINKS

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

MATHEMATICA

nr7Q[n_]:=Module[{trms=NestWhileList[If[EvenQ[#], #/2, #+1]&, n, #!=1&]}, Length[ trms]>4 && trms[[-5]]==7]; Select[Range[8, 220], nr7Q] (* Harvey P. Dale, Oct 10 2017 *)

PROG

(PARI) xnp1(n, p) = { for(x=1, n, p1 = x; while(p1>1, if(p1%2==0, p1/=2, p1 = p1*p+1; ); if(p1==7, print1(x" ")) ) ) }

CROSSREFS

Sequence in context: A293817 A296795 A079831 * A112653 A301660 A022103

Adjacent sequences:  A022800 A022801 A022802 * A022804 A022805 A022806

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Mar 23 2003

STATUS

approved

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Last modified November 18 14:59 EST 2019. Contains 329262 sequences. (Running on oeis4.)