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 A195328 #12 May 09 2021 02:17:39 %S A195328 2,4,6,18,50,54,162,242,450,486,882,1058,1782,3042,3078,4050,5202, %T A195328 9522,19602,22050,36450,46818,54450,66978,71442,95922,124002,149058, %U A195328 183618,190962,238050,240570,263538,277830,328050,466578,684450,816642,977202 %N A195328 Number of bases to which terms of A141768 are strong pseudoprimes. %H A195328 Charles R Greathouse IV, <a href="/A195328/b195328.txt">Table of n, a(n) for n = 1..5476</a> %H A195328 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a> %o A195328 (PARI) star(n)={n--; n>>valuation(n, 2)}; %o A195328 bases(n)=my(f=factor(n)[, 1], nu=valuation(f[1]-1, 2), nn = star(n)); for(i=2, #f, nu = min(nu, valuation(f[i] - 1, 2)); ); (1 + (2^(#f * nu) - 1) / (2^#f - 1)) * prod(i=1, #f, gcd(nn, star(f[i]))); \\ Given a value of A141768, this function transforms it to a term of this sequence. %Y A195328 Cf. A141768, A195327. %K A195328 nonn %O A195328 1,1 %A A195328 _Charles R Greathouse IV_, Sep 15 2011