1,2

A046951(a(n)) = n and A046951(m) <> n for m < a(n);

all terms are smooth squares: if prime(k) is a factor of a(n) then also prime(i) are factors, i<k;

a(p) = 2^(2*(p-1)) for primes p;

if prime(j) is the greatest prime factor of a(n) then a(2*n) = a(n)*prime(j+1)^2;

A001221(a(n)) = A122375(n); A001222(a(n)) = 2*A122376(n).

Eric Weisstein's World of Mathematics, Smooth Number

Sequence in context: A136404 A046952 A081456 this_sequence A030158 A054246 A080709

Adjacent sequences: A130276 A130277 A130278 this_sequence A130280 A130281 A130282

nonn

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 20 2007