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 A104137 #15 Jul 02 2025 16:02:02
%S A104137 4,8,18,126,380,4112,14310,184410,9272780,34669602,1857545300,
%T A104137 26818405352,102282248574,1497215711538,84973644983780,
%U A104137 4885261149611790,18900353608280300,1101298162244236182,16628051030379615882
%N A104137 Number of distinct necklaces with p beads of two possible colors, allowing turning over, p being a prime greater than 2.
%C A104137 For the general necklace problem, see A000029.
%D A104137 Martin Gardner, The Colossal Book of Mathematics, pp. 19, W. W. Norton & Co., NY 2001 (or, New Mathematical Diversions, pp. 243-4 MAA Washington DC 1995).
%F A104137 a(n) = (2^(p-1) - 1)/p + 2^{(p-1)/2} + 1 = A007663(n) + A061285(n) + 1.
%p A104137 for p from 2 to 30 do printf(`%d,`,(2^(ithprime(p)-1)-1)/ithprime(p) + 2^((ithprime(p)-1)/2) + 1) od: # _James Sellers_, Apr 10 2005
%Y A104137 Cf. A000029.
%K A104137 nonn
%O A104137 1,1
%A A104137 _Lekraj Beedassy_, Mar 07 2005
%E A104137 More terms from _James Sellers_, Apr 10 2005