

A177880


Numbers such that not all exponents in prime power factorization are in A005836


1



4, 9, 12, 18, 20, 25, 28, 32, 36, 44, 45, 49, 50, 52, 60, 63, 64, 68, 72, 75, 76, 84, 90, 92, 96, 98, 99, 100, 108, 116, 117, 121, 124, 126, 128, 132, 140, 144, 147, 148, 150, 153, 156, 160, 164, 169, 171, 172, 175, 180, 188, 192, 196, 198, 200, 204, 207
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OFFSET

1,1


COMMENTS

1 and products of distinct numbers of the form P^(3^k), k>=0, are not in the sequence.


LINKS

Table of n, a(n) for n=1..57.


FORMULA

Let A(x) be counting function of terms not exceeding x. Then for x tends to infinity, A(x)=C*x+o(x^(0.5+eps), where C=1Prod{i=p^(3^k)with prime p and k>=0}(11/(i^2+i+1)).


PROG

(Sage) is_A005836 = lambda n: 2 not in n.digits(base=3)
is_A177880 = lambda n: not all(is_A005836(Integer(m)) for p, m in factor(n)) # [D. S. McNeil, Dec 16 2010]


CROSSREFS

Cf. A005836
Sequence in context: A276885 A089910 A312862 * A059269 A081619 A304365
Adjacent sequences: A177877 A177878 A177879 * A177881 A177882 A177883


KEYWORD

nonn


AUTHOR

Vladimir Shevelev, Dec 15 2010


EXTENSIONS

Extended by D. S. McNeil, Dec 16 2010


STATUS

approved



