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 A259990 #12 Jul 18 2015 14:48:56 %S A259990 7,49,2401,2401,386561,5764801,58471553,374712065,4802079233, %T A259990 149429406721,1595702681601,42091354378241,665724390506497, %U A259990 10190301669556225,99086356274020353,1654767311852142593,14722487338708369409,228161914444026740737,2789435039707847196673 %N A259990 This sequence and A259991 are base-14 analogs of A007185 and A016090, written in base 10. %C A259990 See Schut (1991) for precise definition. %C A259990 Ignoring repetitions, the subsequence of A201919 of terms ending in 7 in base 14. - _Eric M. Schmidt_, Jul 18 2015 %D A259990 C. P. Schut, Idempotents. Report AM-R9101, Centrum voor Wiskunde en Informatica, Amsterdam, 1991. %H A259990 Eric M. Schmidt, <a href="/A259990/b259990.txt">Table of n, a(n) for n = 1..500</a> %o A259990 (Sage) def a(n) : return crt(1, 0, 2^n, 7^n) # _Eric M. Schmidt_, Jul 18 2015 %Y A259990 Cf. A007185, A016090, A201919, A259986-A259991. %K A259990 nonn,base %O A259990 1,1 %A A259990 _N. J. A. Sloane_, Jul 13 2015 %E A259990 More terms from _Eric M. Schmidt_, Jul 18 2015