OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
MATHEMATICA
a[n_] := MemberQ[Partition[NestWhileList[If[EvenQ[#], #/2, # + 1] &, 10^n, # != 1 &], 5, 1], {7, 8, 4, 2, 1}]; Select[Range[500], a] (* G. C. Greubel, Apr 12 2017 *)
PROG
(PARI) xnp10(n, p) = { for(x=1, n, p10 = 10^x; while(p10>1, if(p10%2==0, p10/=2, p10 = p10*p+1; ); if(p10==7, print1(x" ")) ) ) }
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Mar 23 2003
STATUS
approved