A080947 Numbers having more than three divisors that are also suffixes in binary representation.

63, 126, 231, 252, 255, 363, 399, 462, 495, 504, 510, 567, 627, 726, 735, 759, 798, 845, 891, 903, 924, 975, 990, 1008, 1020, 1023, 1071, 1134, 1215, 1239, 1254, 1365, 1407, 1419, 1452, 1455, 1470, 1518, 1575, 1596, 1690, 1695, 1743, 1755, 1782, 1806, 1848

Offset

1,1

Comments

A080942(a(n))>3.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Example

a(4) = 252: divisors(252) = {1, 2, 3, 4->'100', 6, 7, 9, 12->'1100', 14, 18, 21, 28->'11100', 36, 42, 63, 84, 126, 252->'11111100'}: A080946(252) = #{4, 12, 28, 252} = 4;
a(15) = 735: divisors(735) = {1->'1', 3->'11', 5, 7->'111', 15->'1111', 21, 35, 49, 105, 147, 245, 735->'1011011111'}: A080942(735) = #{1, 3, 7, 15, 735} = 5.

Prog

(Haskell)
a080947 n = a080947_list !! (n-1)
a080947_list = filter ((> 3) . a080942) [1..]
-- Reinhard Zumkeller, Mar 27 2014

Crossrefs

Cf. A080946, A007088, A080940, A080941.

Sequence in context: A096023 A256813 A324488 * A023720 A031468 A045064

Adjacent sequences: A080944 A080945 A080946 * A080948 A080949 A080950

Keyword

nonn,base

Author

Reinhard Zumkeller, Feb 25 2003

Status

approved