A028389 The 5x + 1 sequence beginning at 7.

7, 36, 18, 9, 46, 23, 116, 58, 29, 146, 73, 366, 183, 916, 458, 229, 1146, 573, 2866, 1433, 7166, 3583, 17916, 8958, 4479, 22396, 11198, 5599, 27996, 13998, 6999, 34996, 17498, 8749, 43746, 21873, 109366, 54683, 273416, 136708, 68354, 34177, 170886, 85443, 427216

Offset

0,1

Links

Alois P. Heinz, Table of n, a(n) for n = 0..10000

Formula

a(0) = 7; a(n) = 5*a(n-1) + 1 if a(n-1) is odd, a(n) = a(n-1)/2 otherwise.

Maple

f := proc(n) option remember; if n = 0 then 7 elif f(n-1) mod 2 = 0 then f(n-1)/2 else 5*f(n-1)+1; fi; end; seq(f(n), n=0..50);

Mathematica

a[0] = 7; a[n_] := a[n] = If[OddQ[a[n-1]], 5 a[n-1] + 1, a[n-1]/2];
a /@ Range[0, 50] (* Jean-François Alcover, Nov 03 2020 *)
NestList[If[OddQ[#], 5#+1, #/2]&, 7, 50] (* Harvey P. Dale, Nov 03 2022 *)

Crossrefs

Cf. A259207, A328010, A328011.

Sequence in context: A364454 A197555 A362162 * A041603 A176543 A018199

Adjacent sequences: A028386 A028387 A028388 * A028390 A028391 A028392

Keyword

nonn

Author

N. J. A. Sloane, Dean Hickerson

Extensions

Named edited by Andrew Howroyd, Aug 21 2020

Status

approved