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 A004654 #23 Feb 22 2019 01:33:45 %S A004654 1,2,4,8,11,22,44,88,121,242,484,918,1331,2662 %N A004654 Powers of 2 written in base 15. (Next term contains a non-decimal character.) %C A004654 a(14) is defined as "2^14 written in base 15". However, the base-15 digits of 2^14 are [4,12,12,4]. The standard convention of using letters A, B, ... to represent digits > 9, cannot be used in the Data sections of OEIS entries. One possibility to encode such terms within the given constraints and without affecting the earlier terms would be to use 00, 10, 20, ..., 50 to represent unambiguously the digits 0, 10, 11, ..., 14. - _M. F. Hasler_, Jun 22 2018. %C A004654 This sequence makes a nice puzzle. It would be possible to allow non-decimal characters by using pairs of decimal digits instead of single digits, but this would spoil the beauty of the puzzle. - _N. J. A. Sloane_, Jun 25 2018 %o A004654 (PARI) apply( a(n,b=15,m=2)=fromdigits(digits(m^n,b)), [0..13]) \\ This sums the base-15 digits multiplied by powers of 10. Digits > 9 occurring for n >= 14 will carry over to the left (4CC4 -> 5324). - _M. F. Hasler_, Jun 22 2018 %Y A004654 Cf. A000079, A004643, ..., A004655: powers of 2 written in base 10, 4, 5, ..., 16. %Y A004654 Cf. A000244, A004656, A004658, A004659, ...: powers of 3 in base 10, 2, 4, 5, ... %K A004654 nonn,base %O A004654 0,2 %A A004654 _N. J. A. Sloane_