This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A381215 #19 Feb 21 2025 09:31:32
%S A381215 2,8,9,36,72,81,108,216,625,15625,117649,5764801,25937424601,
%T A381215 3138428376721,23298085122481,3937376385699289,48661191875666868481,
%U A381215 14063084452067724991009,104127350297911241532841,37589973457545958193355601,907846434775996175406740561329
%N A381215 Numbers k such that the difference between the largest and smallest element of the set of bases and exponents (including exponents = 1) in the prime factorization of k is 1.
%H A381215 Paolo Xausa, <a href="/A381215/b381215.txt">Table of n, a(n) for n = 1..155</a>
%F A381215 For n >= 9, a(n) = A381317(n-4).
%e A381215 72 is a term because 72 = 2^3*3^2, the set of these bases and exponents is {2, 3} and 3 - 2 = 1.
%t A381215 Join[{2, 8, 9, 36, 72, 81, 108, 216}, Flatten[Map[#^{# - 1, # + 1} &, Prime[Range[3, 10]]]]]
%Y A381215 Positions of ones in A381214.
%Y A381215 Cf. A036878, A081812, A104126, A381212, A381317.
%K A381215 nonn,easy
%O A381215 1,1
%A A381215 _Paolo Xausa_, Feb 19 2025