

A111907


A number n is included if the same number of primes, among primes <= the largest prime dividing n, divide n as do not.


2



1, 3, 9, 14, 21, 27, 28, 35, 56, 63, 78, 81, 98, 112, 130, 147, 156, 175, 182, 189, 195, 196, 224, 234, 243, 245, 260, 273, 286, 312, 364, 392, 429, 441, 448, 455, 468, 520, 567, 570, 572, 585, 624, 650, 686, 702, 715, 728, 729, 784, 798, 819, 875, 896, 936
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..55.


EXAMPLE

28 is included because 7 is the largest prime dividing 28. And of the primes <= 7 (2,3,5,7), 2 and 7 (2 primes) divide 28 and 3 and 5 (also 2 primes) do not divide 28.


PROG

(PARI) {m=950; v=vector(m); for(n=1, m, f=factor(n)[, 1]~; c=0; pc=0; forprime(p=2, vecmax(f), j=1; s=length(f); while(j<=s&&p!=f[j], j++); if(j<=s, c++); pc++); v[n]=sign(pc2*c)); for(n=1, m, if(v[n]==0, print1(n, ", ")))} (Klaus Brockhaus)


CROSSREFS

Cf. A111905, A111906.
Sequence in context: A103813 A001968 A305373 * A309149 A294480 A195972
Adjacent sequences: A111904 A111905 A111906 * A111908 A111909 A111910


KEYWORD

nonn


AUTHOR

Leroy Quet, Aug 19 2005


EXTENSIONS

More terms from Klaus Brockhaus, Aug 21 2005


STATUS

approved



