cp's OEIS Frontend

A278248 Least number with the same prime signature as the n-th number in Perrin sequence: a(n) = A046523(A001608(n)), a(1) = 0.

%I A278248 #15 Nov 19 2016 08:30:39
%S A278248 2,0,2,2,2,2,2,2,6,12,2,6,2,6,6,12,60,6,6,6,2,2,96,60,2,30,6,6,6,840,
%T A278248 30,6,30,6,2,6,6,60,2,420,1260,30,30,420,210,30,30,210,6,30,30,12,6,
%U A278248 2310,30,840,6,240,6,30,6,420,6,6,30,420,6,210,6,6,6,4620,60,210,30030,2,6,30,2310,13860,60,210,6,6,6,120,6,2310,210,210,6,210,30,60,4620
%N A278248 Least number with the same prime signature as the n-th number in Perrin sequence: a(n) = A046523(A001608(n)), a(1) = 0.
%C A278248 This sequence works as a "sentinel" for Perrin sequence by matching to any other sequence that is obtained as f(A001608(n)), where f(n) is any function that depends only on the prime signature of n (see the index entry for "sequences computed from exponents in ..."). As of Nov 11 2016 no such sequences were present in the database.
%H A278248 Antti Karttunen, <a href="/A278248/b278248.txt">Table of n, a(n) for n = 0..555</a>
%H A278248 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>
%F A278248 a(1) = 0; for any other n, a(n) = A046523(A001608(n)).
%o A278248 (PARI)
%o A278248 A046523(n) = my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]) \\ From _Charles R Greathouse IV_, Aug 17 2011
%o A278248 p0 = 3; p1 = 0; p2 = 2; for(n=0, 555, write("b278248.txt", n, " ", if(!p0,p0,A046523(p0))); old_p0 = p0; old_p1 = p1; p0 = p1; p1 = p2; p2 = old_p1 + old_p0; );
%o A278248 (Scheme) (define (A278248 n) (if (= 1 n) 0 (A046523 (A001608 n))))
%Y A278248 Cf. A001608, A046523, A278241, A278245.
%K A278248 nonn
%O A278248 0,1
%A A278248 _Antti Karttunen_, Nov 16 2016