

A072688


Of the first n integers (inclusive), how many of them have a prime number of letters in their English names?


0



1, 2, 3, 3, 3, 4, 5, 6, 6, 7, 7, 7, 7, 7, 8, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 12, 13, 13, 13, 13, 13, 14, 14, 14, 14, 15, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..70.


FORMULA

a(n)=number of terms of A072685 <= n.


EXAMPLE

Sequence A072685 begins: 1, 2, 3, 6, 7, 8, 10 so there are 3 terms up to and including n=4, 3 terms up to and including n=5, 6 terms up to and including n=9. Therefore a(4)=3, a(5)=3, a(9)=6.


CROSSREFS

Cf. A072685, A072687.
Sequence in context: A037458 A296816 A064474 * A120504 A025772 A211535
Adjacent sequences: A072685 A072686 A072687 * A072689 A072690 A072691


KEYWORD

easy,nonn,word


AUTHOR

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 02 2002


STATUS

approved



