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A036314
Composite numbers whose prime factors contain no digits other than 3 and 4.
2
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
OFFSET
1,1
COMMENTS
All terms are a product of at least two terms of A020461. - David A. Corneth, Oct 09 2020
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
KEYWORD
nonn,easy,base
AUTHOR
Patrick De Geest, Dec 15 1998
STATUS
approved