OFFSET
1,1
COMMENTS
A006577(n) is the number of halving and tripling steps to reach 1 in the '3x+1' problem.
The distinct squares in the sequence are 9, 25, 36, 49, 169, 361, ...
The distinct primes in the sequence are 2, 3, 7, 11, 31, 41, 47, 71, 73, 97, 103, ...
LINKS
MAPLE
nn:=3*10^6:U:=array(1..nn):V:=array(1..nn):
for i from 1 to nn do:
m:=i:it0:=0:
for j from 1 to nn while(m<>1) do:
if irem(m, 2)=0
then
m:=m/2:it0:=it0+1:
else
m:=3*m+1:it0:=it0+1:
fi:
od:
U[i]:=it0:
od:
for n from 1 to 60 do:
ii:=0:
for k from 1 to nn while(ii=0) do:
if U[k]=U[n]+ U[n+1]
then
ii:=1:printf(`%d, `, k):
else
fi:
od:
od:
MATHEMATICA
f:=Table[Length[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #!=1&]]-1, {n, 3*10^6}]; Do[k=1; While[f[[k]]!=f[[m]]+f[[m+1]], k++]; Print[m, " ", k], {m, 1, 60}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Nov 06 2016
STATUS
approved