cp's OEIS Frontend

A381492 a(n) is the logarithm to base A381491(n) of A381487(n).

%I A381492 #16 Feb 27 2025 10:48:03
%S A381492 0,1,1,1,1,1,1,1,1,1,2,7,4,3,3,4,4,13,7,5,5,7,19,6,7,10,7,7,25,8,13,9,
%T A381492 10,9,13,31,10,16,11,11,13,37,19,12,13,13,43,22,19,14,16,15,15,49,25,
%U A381492 16,17,19,17,55,28,19,18,25,19,61,22,31,21,20,21,67,34,23,22,25
%N A381492 a(n) is the logarithm to base A381491(n) of A381487(n).
%H A381492 Michel Marcus, <a href="/A381492/b381492.txt">Table of n, a(n) for n = 1..3347</a>
%e A381492 a(12) = 7 since A381487(12) = 128 = 2^7 = A381491(12)^a(12).
%t A381492 A010888[n_]:=n - 9*Floor[(n-1)/9]; kmax=5*10^6; a={0,1}; For[k=2, k<=kmax, k++, If[A010888[k]!=1, If[IntegerQ[e=Log[A010888[k],k]], AppendTo[a,e]]]]; a
%o A381492 (PARI) dr(n) = if(n, (n-1)%9+1); \\ A010888
%o A381492 expo(n, k) = if (n<=1, n, logint(n, k));
%o A381492 lista(nn) = my(list = List()); listput(list, 0); listput(list, 1); for (n=2, 9, for (k=1, logint(nn, n), if (dr(n^k) == n, listput(list, n^k)););); my(w=vecsort(Vec(list)), ws=apply(x->dr(x), w)); vector(#w, k, expo(w[k], ws[k])); \\ _Michel Marcus_, Feb 27 2025
%Y A381492 Cf. A381487, A381491.
%K A381492 nonn,base
%O A381492 1,11
%A A381492 _Stefano Spezia_, Feb 25 2025
%E A381492 More terms from _Michel Marcus_, Feb 27 2025