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 A282090 #13 Feb 08 2017 11:51:54 %S A282090 40,156,400,820,1464,2380,3280,3616,3906,5220,7240,9724,12720,19608, %T A282090 20440,25260,30784,37060,60880,66430,70644,81400,93196,97656,106080, %U A282090 120100,135304,151740,169456,177156,188500,254080,265720,278916,333340,363024,394420,427576,462540,499360 %N A282090 Totient numbers (A002202) of the form 1 + k + k^2 + k^3 +...+ k^i (i > 1, k > 1). %C A282090 Totient numbers of the form (k^(i+1) - 1)/(k - 1) where k and i are both odd numbers that are greater than 1. %H A282090 Charles R Greathouse IV, <a href="/A282090/b282090.txt">Table of n, a(n) for n = 1..10000</a> %e A282090 40 is a term because 1 + 3 + 9 + 27 = 40 is a totient number. %o A282090 (PARI) list(lim)=my(v=List(), e, t); for(b=2, sqrt(lim), e=3; while((t=(b^e-1)/(b-1))<=lim, if(istotient(t),listput(v, t)); e++)); vecsort(Vec(v), , 8) \\ _Ray Chandler_, Feb 08 2017 %Y A282090 Intersection of A002202 and A053696. %Y A282090 Cf. A281962. %K A282090 nonn %O A282090 1,1 %A A282090 _Altug Alkan_, Feb 06 2017 %E A282090 Terms confirmed by _Ray Chandler_, Feb 08 2017