A230289 Let m = n-th number not divisible by 3 (A001651); a(n) = position of m in A065075, or -1 if never appears in A065075.

1, 3, 4, 7, 6, 5, 8, 9, 10, 13, 24, 41, 26, 51, 64, 151, 276, 335, 446, 219, 550, 451, 1674, 1685, 2192, 2667, 9220, 17647, 3972, 9221, 17648, 25311, 35776, 25339, 147018, 112397, 146972, 212667, 243892, 243871, 963024, 1263521, 1838078, 2380569, 2380378

Offset: 1

Author

N. J. A. Sloane, Oct 17 2013

Keywords

• nonn
• base

Comments

It is believed that a(n) is always > 0.

Links

• Lars Blomberg, Table of n, a(n) for n = 1..86
• Index entries for Colombian or self numbers and related sequences

Crossrefs

Cf. A065075, A001651.

Programs

Maple

read transforms; M:=100000; sp:=1; a:=[sp]; s:=sp;
for n from 2 to M do sp:=digsum(s); a:=[op(a),sp]; s:=s+sp; od:
b:=[]:
for n from 1 to 100 do
if (n mod 3) <> 0 then
if member(n,a,'p') then b:=[op(b),p] else b:=[op(b),-1]; fi;
fi;
od:
b;

Extensions

a(35)-a(45) from Lars Blomberg, Jul 31 2017