A171862 Index of first occurrence of n in A181391, or 0 if n never appears.

1, 3, 5, 20, 17, 12, 10, 66, 47, 24, 148, 44, 173, 121, 30, 35, 138, 41, 63, 89, 56, 105, 324, 101, 215, 110, 257, 142, 320, 225, 471, 72, 59, 81, 183, 539, 134, 92, 263, 168, 129, 548, 52, 199, 179, 228, 98, 297, 621, 670, 357, 156, 116, 1486, 475

Offset: 0

Author

N. J. A. Sloane, Oct 17 2010

Keywords

• nonn

Links

• N. J. A. Sloane and Reinhard Zumkeller, Table of n, a(n) for n = 0..10000 (terms 1..1594 from N. J. A. Sloane)

Crossrefs

Cf. A181391, A171863, A171864.

Programs

Haskell

import Data.List (elemIndex)
import Data.Maybe (fromJust)
a171862 n = 1 + fromJust (elemIndex n a181391_list)
-- Reinhard Zumkeller, Oct 31 2011

Mathematica

nmax = 100;
seq[m_] := seq[m] = Module[{b, last}, b[] = 0; last[] = -1; last[0] = 2; nxt = 1; Do[hist = last[nxt]; b[n] = nxt; last[nxt] = n; nxt = 0; If[hist > 0, nxt = n - hist], {n, 3, m}];
 A171862 = Array[b, m];
 a[n_] := FirstPosition[A171862, n];
 Table[a[n], {n, 0, nmax}] /. Missing["NotFound"] -> 0 // Flatten
];
seq[m = nmax];
seq[m = 2 m];
While[Print["m = ", m]; seq[m] != seq[m/2], m = 2 m;];
seq[m] (* Jean-François Alcover, Aug 02 2018, borrowing some Maple code from N. J. A. Sloane *)

Extensions

Offset corrected by Reinhard Zumkeller, Oct 31 2011