A036317 Composite numbers whose prime factors contain no digits other than 3 and 8.

9, 27, 81, 243, 249, 729, 747, 1149, 2187, 2241, 2649, 3447, 6561, 6723, 6889, 7947, 10341, 11499, 19683, 20169, 20667, 23841, 31023, 31789, 34497, 59049, 60507, 62001, 71523, 73289, 93069, 95367, 103491, 114999, 116499, 146689, 177147

Offset

1,1

Comments

All terms are a product of at least two terms of A020464. - David A. Corneth, Oct 09 2020

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Index entries for sequences related to prime factors.

Formula

Sum_{n>=1} 1/a(n) = Product_{p in A020464} (p/(p - 1)) - Sum_{p in A020464} 1/p - 1 = 0.1750565813... . - Amiram Eldar, May 22 2022

Crossrefs

Cf. A020464, A036302-A036325.

Sequence in context: A036314 A215690 A255623 * A053762 A126322 A020279

Adjacent sequences: A036314 A036315 A036316 * A036318 A036319 A036320

Keyword

nonn,easy,base

Author

Patrick De Geest, Dec 15 1998

Status

approved