A036314 - OEIS

A036314

Composite numbers whose prime factors contain no digits other than 3 and 4.

9, 27, 81, 129, 243, 387, 729, 1161, 1299, 1329, 1849, 2187, 3483, 3897, 3987, 5547, 6561, 10029, 10299, 10449, 11691, 11961, 16641, 18619, 19049, 19683, 30087, 30897, 31347, 35073, 35883, 49923, 55857, 57147, 59049, 79507, 90261, 92691

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OFFSET

1,1

COMMENTS

All terms are a product of at least two terms of A020461. - 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 A020461} (p/(p - 1)) - Sum_{p in A020461} 1/p - 1 = 0.1819438988... . - Amiram Eldar, May 22 2022

CROSSREFS

Cf. A020461, A036302-A036325.

Sequence in context: A264959 A370870 A053702 * A215690 A255623 A036317

Adjacent sequences: A036311 A036312 A036313 * A036315 A036316 A036317

KEYWORD

nonn,easy,base

AUTHOR

Patrick De Geest, Dec 15 1998

STATUS

approved