A246063 First occurrence of n in sequence A112329.

2, 1, 3, 9, 15, 64, 45, 256, 96, 144, 192, 4096, 240, 16384, 768, 576, 480, 262144, 720, 1048576, 960, 2304, 12288, 16777216, 1440, 5184, 49152, 3600, 3840, 1073741824, 2880, 4294967296, 3360, 36864, 786432, 20736, 5040, 274877906944, 3145728, 147456, 6720

Offset

0,1

Comments

Inspired by a comment from Robert G. Wilson v in sequence A112329.

Links

Ray Chandler, Table of n, a(n) for n = 0..3322 [terms <= 1000 digits]

Formula

a(p) = 2^(p+1) for prime p >= 5.

Mathematica

g[lst_, p_]:=Module[{t, i, j}, Union[Flatten[Table[t=lst[[i]]; t[[j]]=p*t[[j]]; Sort[t], {i, Length[lst]}, {j, Length[lst[[i]]]}], 1], Table[Sort[Append[lst[[i]], p]], {i, Length[lst]}]]]; f[n_]:=Module[{i, j, p, e, lst={{}}}, {p, e}=Transpose[FactorInteger[n]]; Do[lst=g[lst, p[[i]]], {i, Length[p]}, {j, e[[i]]}]; lst];
(* above factor functions from T. D. Noe in A162247 *)
nmax=100;
a1={2, 1, 3};
Do[
least=Infinity;
fn=f[n];
Do[
exps=Reverse[fnitem]-1;
odd=even=1;
cnt=0;
Do[
cnt++;
odd*=(Prime[cnt+1]^exp);
even*=(Prime[cnt]^exp);
, {exp, exps}];
least=Min[least, odd, 4even];
, {fnitem, fn}];
AppendTo[a1, least];
, {n, 3, nmax}];
a1

Prog

(PARI) d(n) = if (denominator(n)==1, numdiv(n), 0);
f(n) = numdiv(n) - 2*d(n/2) + 2*d(n/4);
a(n) = {my(k = 1); while (f(k) != n, k++); k; } \\ Michel Marcus, Jul 30 2017

Crossrefs

Cf. A094572, A112329.

Sequence in context: A249632 A126009 A301282 * A332064 A229417 A337890

Adjacent sequences: A246060 A246061 A246062 * A246064 A246065 A246066

Keyword

nonn

Author

Ray Chandler, Aug 24 2014

Status

approved