cp's OEIS Frontend

A243056 If n is the i-th prime, p_i = A000040(i), then a(n) = i, otherwise the difference between the indices of the smallest and the largest prime dividing n: for n = p_i * ... * p_k, where p_i <= ... <= p_k, a(n) = (k-i); a(1) = 0 by convention.

%I A243056 #10 Jun 01 2014 00:14:26
%S A243056 0,1,2,0,3,1,4,0,0,2,5,1,6,3,1,0,7,1,8,2,2,4,9,1,0,5,0,3,10,2,11,0,3,
%T A243056 6,1,1,12,7,4,2,13,3,14,4,1,8,15,1,0,2,5,5,16,1,2,3,6,9,17,2,18,10,2,
%U A243056 0,3,4,19,6,7,3,20,1,21,11,1,7,1,5,22,2,0,12,23,3,4,13,8,4,24,2
%N A243056 If n is the i-th prime, p_i = A000040(i), then a(n) = i, otherwise the difference between the indices of the smallest and the largest prime dividing n: for n = p_i * ... * p_k, where p_i <= ... <= p_k, a(n) = (k-i); a(1) = 0 by convention.
%H A243056 Antti Karttunen, <a href="/A243056/b243056.txt">Table of n, a(n) for n = 1..10000</a>
%F A243056 a(1) = 0, for n>1, if n = A000040(i), a(n) = i, otherwise a(n) = A061395(n) - A055396(n) = A243055(n).
%o A243056 (Scheme) (define (A243056 n) (if (prime? n) (A049084 n) (A243055 n)))
%Y A243056 Useful when computing A243057 or A243059.
%Y A243056 A025475 (prime powers that are not primes) gives the positions of zeros.
%Y A243056 Differs from A241917 for the first time at n=18.
%Y A243056 Cf. A243055, A241919, A242411, A049084, A027748, A055396, A061395.
%K A243056 nonn
%O A243056 1,3
%A A243056 _Antti Karttunen_, May 31 2014