cp's OEIS Frontend

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.

A317725 a(n) is the smallest k > 1 whose sum of digits is the same in all the bases from 2 to n.

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%I A317725 #15 Sep 03 2023 10:40:58
%S A317725 2,6,21,23162843828305
%N A317725 a(n) is the smallest k > 1 whose sum of digits is the same in all the bases from 2 to n.
%C A317725 No other terms below 4^60 ~= 1.3*10^36. The sequence is likely finite and complete. - _Max Alekseyev_, Aug 29 2023
%e A317725 a(3) = A037301(3).
%e A317725 a(4) = A135122(2).
%e A317725 a(5) = A317777(2) = 23162843828305 in base 2, 3, 4, and 5 is equal to: 101010001000100000101000101000001000001010001, 10001000100100102010101011001, 11101010011011001001101, and 11014000001010001210, respectively. The sum of the digits is 13 in the 4 cases.
%o A317725 (PARI) isok(k, n) = #Set(vector(n-1, b, b++; sumdigits(k, b))) == 1;
%o A317725 a(n) = my(k=2); while (!isok(k, n), k++); k; \\ _Michel Marcus_, Sep 02 2023
%Y A317725 Cf. A037301, A135122, A317777.
%K A317725 nonn,base,hard,more
%O A317725 2,1
%A A317725 _Giovanni Resta_, Aug 05 2018
%E A317725 a(2) = 2 prepended by _Max Alekseyev_, Aug 29 2023