login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A373094 a(n) is the least number k such that A373092(k) = n. 1
1, 4, 7, 12, 24, 120, 1260, 1829520 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
a(n) is the least number k such that the number of iterations of the map x -> A093653(x) required to reach from k to a fixed point is n.
a(8) > 4*10^10.
LINKS
EXAMPLE
The iterations for the n = 0..7 are:
n a(n) iterations
- ------- --------------------------------------------------
0 1 1
1 4 4 -> 3
2 7 7 -> 4 -> 3
3 12 12 -> 9 -> 5 ->3
4 24 24 -> 12 -> 9 -> 5 -> 3
5 120 120 -> 36 -> 15 -> 9 -> 5 -> 3
6 1260 1260 -> 120 -> 36 -> 15 -> 9 -> 5 -> 3
7 1829520 1829520 -> 1260 -> 120 -> 36 -> 15 -> 9 -> 5 -> 3
MATHEMATICA
d[n_] := d[n] = DivisorSum[n, Plus @@ IntegerDigits[#, 2] &];
f[n_] := -2 + Length@ FixedPointList[d, n];
seq[len_] := Module[{s = Table[0, {len}], c = 0, i, n = 1}, While[c < len, i = f[n] + 1; If[i <= len && s[[i]] == 0, c++; s[[i]] = n]; n++]; s]; seq[7]
PROG
(PARI) f(n) = {my(c = 0); while(6 % n, n = sumdiv(n, d, hammingweight(d)); c++); c; }
lista(len) = {my(s = vector(len), c = 0, i, n = 1); while(c < len, i = f(n) + 1; if(i <= len && s[i] == 0, c++; s[i] = n); n++); s; }
CROSSREFS
Cf. A093653, A095347 (decimal analog), A373092.
Sequence in context: A243860 A322619 A299900 * A215329 A208724 A183336
KEYWORD
nonn,base,hard,more
AUTHOR
Amiram Eldar, May 23 2024
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 24 21:32 EDT 2024. Contains 374585 sequences. (Running on oeis4.)