OFFSET
1,2
COMMENTS
m is in the sequence iff m/10 is already in the sequence or m is a power of 4 or 25.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{n>=1} 1/a(n) = 55/36. - Amiram Eldar, Feb 18 2021
MATHEMATICA
max = 200000; Reap[Do[k = 2^i*5^j; If[k <= max && EvenQ[i + j], Sow[k]], {i, 0, Log[2, max] // Ceiling}, {j, 0, Log[5, max] // Ceiling}]][[2, 1]] // Union (* Amiram Eldar, Feb 18 2021 after Jean-François Alcover at A036667 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Henry Bottomley, May 23 2000
STATUS
approved