cp's OEIS Frontend

A278028 Let {c(i)} = A007916 denote the sequence of numbers > 1 which are not perfect powers. Every positive integer n has a unique representation as a tower n = c(x_1)^c(x_2)^c(x_3)^...^c(x_k), where the exponents are nested from the right. The sequence is an irregular triangle read by rows, where the n-th row lists x_1, ..., x_k.

%I A278028 #36 Jun 17 2017 14:25:40
%S A278028 1,2,1,1,3,4,5,1,2,2,1,6,7,8,9,10,11,1,1,1,12,13,14,15,16,17,18,19,3,
%T A278028 1,20,2,2,21,22,23,24,1,3,25,26,27,4,1,28,29,30,31
%N A278028 Let {c(i)} = A007916 denote the sequence of numbers > 1 which are not perfect powers. Every positive integer n has a unique representation as a tower n = c(x_1)^c(x_2)^c(x_3)^...^c(x_k), where the exponents are nested from the right. The sequence is an irregular triangle read by rows, where the n-th row lists x_1, ..., x_k.
%C A278028 Row lengths are A288636(n). - _Gus Wiseman_, Jun 12 2017
%H A278028 N. J. A. Sloane, <a href="/A278028/b278028.txt">Table of n, a(n) for n = 1..20181</a>
%H A278028 N. J. A. Sloane, <a href="/A278028/a278028.txt">Maple programs for A007916, A278028, A278029, A052409, A089723, A277564</a>
%e A278028 Rows 2 through 32 are:
%e A278028 1,
%e A278028 2,
%e A278028 1, 1,
%e A278028 3,
%e A278028 4,
%e A278028 5,
%e A278028 1, 2,
%e A278028 2, 1,
%e A278028 6,
%e A278028 7,
%e A278028 8,
%e A278028 9,
%e A278028 10,
%e A278028 11,
%e A278028 1, 1, 1,
%e A278028 12,
%e A278028 13,
%e A278028 14,
%e A278028 15,
%e A278028 16,
%e A278028 17,
%e A278028 18,
%e A278028 19,
%e A278028 3, 1,
%e A278028 20,
%e A278028 2, 2,
%e A278028 21,
%e A278028 22,
%e A278028 23,
%e A278028 24,
%e A278028 1, 3,
%e A278028 ...
%Y A278028 See A277564 for another version.
%Y A278028 Cf. A007916, A089723, A277562, A288636.
%K A278028 nonn,tabf
%O A278028 1,2
%A A278028 _N. J. A. Sloane_, Nov 09 2016